{"group":{"id":1,"name":"Community","lockable":false,"created_at":"2012-01-18T18:02:15.000Z","updated_at":"2025-12-14T01:33:56.000Z","description":"Problems submitted by members of the MATLAB Central community.","is_default":true,"created_by":161519,"badge_id":null,"featured":false,"trending":false,"solution_count_in_trending_period":0,"trending_last_calculated":"2025-12-14T00:00:00.000Z","image_id":null,"published":true,"community_created":false,"status_id":2,"is_default_group_for_player":false,"deleted_by":null,"deleted_at":null,"restored_by":null,"restored_at":null,"description_opc":null,"description_html":null,"published_at":null},"problems":[{"id":42494,"title":"Which permutation is it?","description":"Let write some permutations of positive integers.\r\n  \r\n  \r\n    1:    1 2 3 4 5 6 ...\r\n    2:    2 1 3 4 ...\r\n    3:    1 3 2 4 ...\r\n    4:    2 3 1 4 ...\r\n    5:    3 1 2 4 ...\r\n    6:    3 2 1 4 ...\r\n   25:    1 2 3 5 4 ...\r\n  120:    5 4 3 2 1 6 7 ...\r\n\r\nGiven a permutation of integers in range 1:n, return it's index following above pattern.\r\n\r\nSee also: \u003chttp://nl.mathworks.com/matlabcentral/cody/problems/42495-n-th-permutation 42495\u003e","description_html":"\u003cp\u003eLet write some permutations of positive integers.\u003c/p\u003e\u003cpre\u003e    1:    1 2 3 4 5 6 ...\r\n    2:    2 1 3 4 ...\r\n    3:    1 3 2 4 ...\r\n    4:    2 3 1 4 ...\r\n    5:    3 1 2 4 ...\r\n    6:    3 2 1 4 ...\r\n   25:    1 2 3 5 4 ...\r\n  120:    5 4 3 2 1 6 7 ...\u003c/pre\u003e\u003cp\u003eGiven a permutation of integers in range 1:n, return it's index following above pattern.\u003c/p\u003e\u003cp\u003eSee also: \u003ca href = \"http://nl.mathworks.com/matlabcentral/cody/problems/42495-n-th-permutation\"\u003e42495\u003c/a\u003e\u003c/p\u003e","function_template":"function idx = whichone(P)\r\n  idx = P(1);\r\nend","test_suite":"%%\r\nx = 1;\r\ny_correct = 1;\r\nassert(isequal(whichone(x),y_correct))\r\n%%\r\nx = 1:randi(10);\r\ny_correct = 1;\r\nassert(isequal(whichone(x),y_correct))\r\n%%\r\nx = [1 3 2 4];\r\ny_correct = 3;\r\nassert(isequal(whichone(x),y_correct))\r\n%%\r\nx = [1 3 2 4:10];\r\ny_correct = 3;\r\nassert(isequal(whichone(x),y_correct))\r\n%%\r\nx = [4 3 2 1];\r\ny_correct = 24;\r\nassert(isequal(whichone(x),y_correct))\r\n%%\r\nx = [4 3 2 1 5 6 7];\r\ny_correct = 24;\r\nassert(isequal(whichone(x),y_correct))\r\n%%\r\nx = 10:-1:1;\r\ny_correct = prod(x);\r\nassert(isequal(whichone(x),y_correct))\r\n%%\r\nx = 10:-1:1;\r\ny_correct = prod(x);\r\nassert(isequal(whichone(x),y_correct))\r\n%%\r\nx = [6 3 5 1 2 4];\r\ny_correct = 677;\r\nassert(isequal(whichone(x),y_correct));\r\n%%\r\nfor k = 6:15\r\n  r = randperm(k);\r\n  x1 = [r k+1:k+randi(7)];\r\n  x2 = [fliplr(r) k+1:k+randi(7)];\r\n  assert(isequal(whichone(x1)+whichone(x2)-1,factorial(k)))\r\nend","published":true,"deleted":false,"likes_count":2,"comments_count":0,"created_by":14358,"edited_by":null,"edited_at":null,"deleted_by":null,"deleted_at":null,"solvers_count":35,"test_suite_updated_at":null,"rescore_all_solutions":false,"group_id":1,"created_at":"2015-08-06T11:09:37.000Z","updated_at":"2026-04-01T11:34:13.000Z","published_at":"2015-08-06T11:09:37.000Z","restored_at":null,"restored_by":null,"spam":false,"simulink":false,"admin_reviewed":false,"description_opc":"{\"relationships\":[{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/document\",\"targetMode\":\"\",\"relationshipId\":\"rId1\",\"target\":\"/matlab/document.xml\"},{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/output\",\"targetMode\":\"\",\"relationshipId\":\"rId2\",\"target\":\"/matlab/output.xml\"}],\"parts\":[{\"partUri\":\"/matlab/document.xml\",\"relationship\":[],\"contentType\":\"application/vnd.mathworks.matlab.code.document+xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\"?\u003e\\n\u003cw:document xmlns:w=\\\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\\\"\u003e\u003cw:body\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eLet write some permutations of positive integers.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"code\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e\u003c![CDATA[    1:    1 2 3 4 5 6 ...\\n    2:    2 1 3 4 ...\\n    3:    1 3 2 4 ...\\n    4:    2 3 1 4 ...\\n    5:    3 1 2 4 ...\\n    6:    3 2 1 4 ...\\n   25:    1 2 3 5 4 ...\\n  120:    5 4 3 2 1 6 7 ...]]\u003e\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eGiven a permutation of integers in range 1:n, return it's index following above pattern.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eSee also:\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:hyperlink w:docLocation=\\\"http://nl.mathworks.com/matlabcentral/cody/problems/42495-n-th-permutation\\\"\u003e\u003cw:r\u003e\u003cw:t\u003e42495\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:hyperlink\u003e\u003c/w:p\u003e\u003c/w:body\u003e\u003c/w:document\u003e\"},{\"partUri\":\"/matlab/output.xml\",\"contentType\":\"text/xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\" standalone=\\\"no\\\" ?\u003e\u003cembeddedOutputs\u003e\u003cmetaData\u003e\u003cevaluationState\u003emanual\u003c/evaluationState\u003e\u003clayoutState\u003ecode\u003c/layoutState\u003e\u003coutputStatus\u003eready\u003c/outputStatus\u003e\u003c/metaData\u003e\u003coutputArray type=\\\"array\\\"/\u003e\u003cregionArray type=\\\"array\\\"/\u003e\u003c/embeddedOutputs\u003e\"}]}"},{"id":42495,"title":"N-th permutation.","description":"Let write some permutations of positive integers.\r\n\r\n    1:    1 2 3 4 5 6 ...\r\n    2:    2 1 3 4 ...\r\n    3:    1 3 2 4 ...\r\n    4:    2 3 1 4 ...\r\n    5:    3 1 2 4 ...\r\n    6:    3 2 1 4 ...\r\n   25:    1 2 3 5 4 ...\r\n  120:    5 4 3 2 1 6 7 ...\r\n\r\nGiven an index, find appropriate permutation and truncate sorted part on the right side.\r\n\r\nexample:\r\n\r\n  323:    3 5 1 6 4 2 7 8 9 10 ...\r\n  \r\n  \u003e\u003e n = 323;\r\n  \u003e\u003e whichperm(n)\r\n  ans = \r\n         3 5 1 6 4   \r\n\r\nSee also: \u003chttp://nl.mathworks.com/matlabcentral/cody/problems/42494-which-permutation-is-it 42494\u003e\r\n  ","description_html":"\u003cp\u003eLet write some permutations of positive integers.\u003c/p\u003e\u003cpre\u003e    1:    1 2 3 4 5 6 ...\r\n    2:    2 1 3 4 ...\r\n    3:    1 3 2 4 ...\r\n    4:    2 3 1 4 ...\r\n    5:    3 1 2 4 ...\r\n    6:    3 2 1 4 ...\r\n   25:    1 2 3 5 4 ...\r\n  120:    5 4 3 2 1 6 7 ...\u003c/pre\u003e\u003cp\u003eGiven an index, find appropriate permutation and truncate sorted part on the right side.\u003c/p\u003e\u003cp\u003eexample:\u003c/p\u003e\u003cpre class=\"language-matlab\"\u003e323:    3 5 1 6 4 2 7 8 9 10 ...\r\n\u003c/pre\u003e\u003cpre class=\"language-matlab\"\u003e\u0026gt;\u0026gt; n = 323;\r\n\u0026gt;\u0026gt; whichperm(n)\r\nans = \r\n       3 5 1 6 4   \r\n\u003c/pre\u003e\u003cp\u003eSee also: \u003ca href = \"http://nl.mathworks.com/matlabcentral/cody/problems/42494-which-permutation-is-it\"\u003e42494\u003c/a\u003e\u003c/p\u003e","function_template":"function P = whichperm(n)\r\n  P = 1:n;\r\nend","test_suite":"%%\r\nx = 1;\r\ny_correct = [];\r\nassert(isempty(whichperm(x)))\r\n%%\r\nx = 2;\r\ny_correct = 2;\r\nassert(isequal(whichperm(x),y_correct))\r\n%%\r\nx = 3;\r\ny_correct = [1 3];\r\nassert(isequal(whichperm(x),y_correct))\r\n%%\r\nx = 4;\r\ny_correct = [2 3];\r\nassert(isequal(whichperm(x),y_correct))\r\n%%\r\nx = 5;\r\ny_correct = 3;\r\nassert(isequal(whichperm(x),y_correct))\r\n%%\r\nx = 10;\r\ny_correct = [2 3 4];\r\nassert(isequal(whichperm(x),y_correct))\r\n%%\r\nx = 9;\r\ny_correct = [1 3 4];\r\nassert(isequal(whichperm(x),y_correct))\r\n%%\r\nx = 323;\r\ny_correct = [3 5 1 6 4];\r\nassert(isequal(whichperm(x),y_correct))\r\n%%\r\nx = 2015;\r\ny_correct = [4 6 5 3 7];\r\nassert(isequal(whichperm(x),y_correct))\r\n%%\r\nx = 2016;\r\ny_correct = [4 6 5 3 7 2];\r\nassert(isequal(whichperm(x),y_correct))\r\n%%\r\nx = 1234567890;\r\ny_correct = [11 7 3 5 6 12 4 2 8 10 13 9];\r\nassert(isequal(whichperm(x),y_correct))\r\n%%\r\nx = 720;\r\ny_correct = [6 5 4 3 2];\r\nassert(isequal(whichperm(x),y_correct))\r\n%%\r\nx = 721;\r\ny_correct = [1 2 3 4 5 7];\r\nassert(isequal(whichperm(x),y_correct))\r\n%%\r\nx = 13;\r\ny_correct = [1 4];\r\nassert(isequal(whichperm(x),y_correct))\r\n%%\r\nx = 100;\r\ny_correct = [5 2 3];\r\nassert(isequal(whichperm(x),y_correct))\r\n%%\r\nx = 100000000;\r\ny_correct = [6 2 4 9 10 11 3 5 7 12 8];\r\nassert(isequal(whichperm(x),y_correct))\r\n%%\r\nx = 439084801;\r\ny_correct = [12];\r\nassert(isequal(whichperm(x),y_correct))\r\n%%\r\nx = flintmax;\r\ny_correct = [15 12 11 2 1 10 9 4 16 5 18 3 17 14 8 6 7 19];\r\nassert(isequal(whichperm(x),y_correct))","published":true,"deleted":false,"likes_count":2,"comments_count":0,"created_by":14358,"edited_by":null,"edited_at":null,"deleted_by":null,"deleted_at":null,"solvers_count":36,"test_suite_updated_at":"2015-08-07T10:02:05.000Z","rescore_all_solutions":true,"group_id":1,"created_at":"2015-08-06T12:28:43.000Z","updated_at":"2026-03-18T21:50:47.000Z","published_at":"2015-08-06T12:28:43.000Z","restored_at":null,"restored_by":null,"spam":false,"simulink":false,"admin_reviewed":false,"description_opc":"{\"relationships\":[{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/document\",\"targetMode\":\"\",\"relationshipId\":\"rId1\",\"target\":\"/matlab/document.xml\"},{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/output\",\"targetMode\":\"\",\"relationshipId\":\"rId2\",\"target\":\"/matlab/output.xml\"}],\"parts\":[{\"partUri\":\"/matlab/document.xml\",\"relationship\":[],\"contentType\":\"application/vnd.mathworks.matlab.code.document+xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\"?\u003e\\n\u003cw:document xmlns:w=\\\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\\\"\u003e\u003cw:body\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eLet write some permutations of positive integers.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"code\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e\u003c![CDATA[    1:    1 2 3 4 5 6 ...\\n    2:    2 1 3 4 ...\\n    3:    1 3 2 4 ...\\n    4:    2 3 1 4 ...\\n    5:    3 1 2 4 ...\\n    6:    3 2 1 4 ...\\n   25:    1 2 3 5 4 ...\\n  120:    5 4 3 2 1 6 7 ...]]\u003e\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eGiven an index, find appropriate permutation and truncate sorted part on the right side.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eexample:\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"code\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e\u003c![CDATA[323:    3 5 1 6 4 2 7 8 9 10 ...\\n\\n\u003e\u003e n = 323;\\n\u003e\u003e whichperm(n)\\nans = \\n       3 5 1 6 4]]\u003e\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eSee also:\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:hyperlink w:docLocation=\\\"http://nl.mathworks.com/matlabcentral/cody/problems/42494-which-permutation-is-it\\\"\u003e\u003cw:r\u003e\u003cw:t\u003e42494\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:hyperlink\u003e\u003c/w:p\u003e\u003c/w:body\u003e\u003c/w:document\u003e\"},{\"partUri\":\"/matlab/output.xml\",\"contentType\":\"text/xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\" standalone=\\\"no\\\" ?\u003e\u003cembeddedOutputs\u003e\u003cmetaData\u003e\u003cevaluationState\u003emanual\u003c/evaluationState\u003e\u003clayoutState\u003ecode\u003c/layoutState\u003e\u003coutputStatus\u003eready\u003c/outputStatus\u003e\u003c/metaData\u003e\u003coutputArray type=\\\"array\\\"/\u003e\u003cregionArray type=\\\"array\\\"/\u003e\u003c/embeddedOutputs\u003e\"}]}"}],"problem_search":{"errors":[],"problems":[{"id":42494,"title":"Which permutation is it?","description":"Let write some permutations of positive integers.\r\n  \r\n  \r\n    1:    1 2 3 4 5 6 ...\r\n    2:    2 1 3 4 ...\r\n    3:    1 3 2 4 ...\r\n    4:    2 3 1 4 ...\r\n    5:    3 1 2 4 ...\r\n    6:    3 2 1 4 ...\r\n   25:    1 2 3 5 4 ...\r\n  120:    5 4 3 2 1 6 7 ...\r\n\r\nGiven a permutation of integers in range 1:n, return it's index following above pattern.\r\n\r\nSee also: \u003chttp://nl.mathworks.com/matlabcentral/cody/problems/42495-n-th-permutation 42495\u003e","description_html":"\u003cp\u003eLet write some permutations of positive integers.\u003c/p\u003e\u003cpre\u003e    1:    1 2 3 4 5 6 ...\r\n    2:    2 1 3 4 ...\r\n    3:    1 3 2 4 ...\r\n    4:    2 3 1 4 ...\r\n    5:    3 1 2 4 ...\r\n    6:    3 2 1 4 ...\r\n   25:    1 2 3 5 4 ...\r\n  120:    5 4 3 2 1 6 7 ...\u003c/pre\u003e\u003cp\u003eGiven a permutation of integers in range 1:n, return it's index following above pattern.\u003c/p\u003e\u003cp\u003eSee also: \u003ca href = \"http://nl.mathworks.com/matlabcentral/cody/problems/42495-n-th-permutation\"\u003e42495\u003c/a\u003e\u003c/p\u003e","function_template":"function idx = whichone(P)\r\n  idx = P(1);\r\nend","test_suite":"%%\r\nx = 1;\r\ny_correct = 1;\r\nassert(isequal(whichone(x),y_correct))\r\n%%\r\nx = 1:randi(10);\r\ny_correct = 1;\r\nassert(isequal(whichone(x),y_correct))\r\n%%\r\nx = [1 3 2 4];\r\ny_correct = 3;\r\nassert(isequal(whichone(x),y_correct))\r\n%%\r\nx = [1 3 2 4:10];\r\ny_correct = 3;\r\nassert(isequal(whichone(x),y_correct))\r\n%%\r\nx = [4 3 2 1];\r\ny_correct = 24;\r\nassert(isequal(whichone(x),y_correct))\r\n%%\r\nx = [4 3 2 1 5 6 7];\r\ny_correct = 24;\r\nassert(isequal(whichone(x),y_correct))\r\n%%\r\nx = 10:-1:1;\r\ny_correct = prod(x);\r\nassert(isequal(whichone(x),y_correct))\r\n%%\r\nx = 10:-1:1;\r\ny_correct = prod(x);\r\nassert(isequal(whichone(x),y_correct))\r\n%%\r\nx = [6 3 5 1 2 4];\r\ny_correct = 677;\r\nassert(isequal(whichone(x),y_correct));\r\n%%\r\nfor k = 6:15\r\n  r = randperm(k);\r\n  x1 = [r k+1:k+randi(7)];\r\n  x2 = [fliplr(r) k+1:k+randi(7)];\r\n  assert(isequal(whichone(x1)+whichone(x2)-1,factorial(k)))\r\nend","published":true,"deleted":false,"likes_count":2,"comments_count":0,"created_by":14358,"edited_by":null,"edited_at":null,"deleted_by":null,"deleted_at":null,"solvers_count":35,"test_suite_updated_at":null,"rescore_all_solutions":false,"group_id":1,"created_at":"2015-08-06T11:09:37.000Z","updated_at":"2026-04-01T11:34:13.000Z","published_at":"2015-08-06T11:09:37.000Z","restored_at":null,"restored_by":null,"spam":false,"simulink":false,"admin_reviewed":false,"description_opc":"{\"relationships\":[{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/document\",\"targetMode\":\"\",\"relationshipId\":\"rId1\",\"target\":\"/matlab/document.xml\"},{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/output\",\"targetMode\":\"\",\"relationshipId\":\"rId2\",\"target\":\"/matlab/output.xml\"}],\"parts\":[{\"partUri\":\"/matlab/document.xml\",\"relationship\":[],\"contentType\":\"application/vnd.mathworks.matlab.code.document+xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\"?\u003e\\n\u003cw:document xmlns:w=\\\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\\\"\u003e\u003cw:body\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eLet write some permutations of positive integers.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"code\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e\u003c![CDATA[    1:    1 2 3 4 5 6 ...\\n    2:    2 1 3 4 ...\\n    3:    1 3 2 4 ...\\n    4:    2 3 1 4 ...\\n    5:    3 1 2 4 ...\\n    6:    3 2 1 4 ...\\n   25:    1 2 3 5 4 ...\\n  120:    5 4 3 2 1 6 7 ...]]\u003e\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eGiven a permutation of integers in range 1:n, return it's index following above pattern.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eSee also:\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:hyperlink w:docLocation=\\\"http://nl.mathworks.com/matlabcentral/cody/problems/42495-n-th-permutation\\\"\u003e\u003cw:r\u003e\u003cw:t\u003e42495\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:hyperlink\u003e\u003c/w:p\u003e\u003c/w:body\u003e\u003c/w:document\u003e\"},{\"partUri\":\"/matlab/output.xml\",\"contentType\":\"text/xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\" standalone=\\\"no\\\" ?\u003e\u003cembeddedOutputs\u003e\u003cmetaData\u003e\u003cevaluationState\u003emanual\u003c/evaluationState\u003e\u003clayoutState\u003ecode\u003c/layoutState\u003e\u003coutputStatus\u003eready\u003c/outputStatus\u003e\u003c/metaData\u003e\u003coutputArray type=\\\"array\\\"/\u003e\u003cregionArray type=\\\"array\\\"/\u003e\u003c/embeddedOutputs\u003e\"}]}"},{"id":42495,"title":"N-th permutation.","description":"Let write some permutations of positive integers.\r\n\r\n    1:    1 2 3 4 5 6 ...\r\n    2:    2 1 3 4 ...\r\n    3:    1 3 2 4 ...\r\n    4:    2 3 1 4 ...\r\n    5:    3 1 2 4 ...\r\n    6:    3 2 1 4 ...\r\n   25:    1 2 3 5 4 ...\r\n  120:    5 4 3 2 1 6 7 ...\r\n\r\nGiven an index, find appropriate permutation and truncate sorted part on the right side.\r\n\r\nexample:\r\n\r\n  323:    3 5 1 6 4 2 7 8 9 10 ...\r\n  \r\n  \u003e\u003e n = 323;\r\n  \u003e\u003e whichperm(n)\r\n  ans = \r\n         3 5 1 6 4   \r\n\r\nSee also: \u003chttp://nl.mathworks.com/matlabcentral/cody/problems/42494-which-permutation-is-it 42494\u003e\r\n  ","description_html":"\u003cp\u003eLet write some permutations of positive integers.\u003c/p\u003e\u003cpre\u003e    1:    1 2 3 4 5 6 ...\r\n    2:    2 1 3 4 ...\r\n    3:    1 3 2 4 ...\r\n    4:    2 3 1 4 ...\r\n    5:    3 1 2 4 ...\r\n    6:    3 2 1 4 ...\r\n   25:    1 2 3 5 4 ...\r\n  120:    5 4 3 2 1 6 7 ...\u003c/pre\u003e\u003cp\u003eGiven an index, find appropriate permutation and truncate sorted part on the right side.\u003c/p\u003e\u003cp\u003eexample:\u003c/p\u003e\u003cpre class=\"language-matlab\"\u003e323:    3 5 1 6 4 2 7 8 9 10 ...\r\n\u003c/pre\u003e\u003cpre class=\"language-matlab\"\u003e\u0026gt;\u0026gt; n = 323;\r\n\u0026gt;\u0026gt; whichperm(n)\r\nans = \r\n       3 5 1 6 4   \r\n\u003c/pre\u003e\u003cp\u003eSee also: \u003ca href = \"http://nl.mathworks.com/matlabcentral/cody/problems/42494-which-permutation-is-it\"\u003e42494\u003c/a\u003e\u003c/p\u003e","function_template":"function P = whichperm(n)\r\n  P = 1:n;\r\nend","test_suite":"%%\r\nx = 1;\r\ny_correct = [];\r\nassert(isempty(whichperm(x)))\r\n%%\r\nx = 2;\r\ny_correct = 2;\r\nassert(isequal(whichperm(x),y_correct))\r\n%%\r\nx = 3;\r\ny_correct = [1 3];\r\nassert(isequal(whichperm(x),y_correct))\r\n%%\r\nx = 4;\r\ny_correct = [2 3];\r\nassert(isequal(whichperm(x),y_correct))\r\n%%\r\nx = 5;\r\ny_correct = 3;\r\nassert(isequal(whichperm(x),y_correct))\r\n%%\r\nx = 10;\r\ny_correct = [2 3 4];\r\nassert(isequal(whichperm(x),y_correct))\r\n%%\r\nx = 9;\r\ny_correct = [1 3 4];\r\nassert(isequal(whichperm(x),y_correct))\r\n%%\r\nx = 323;\r\ny_correct = [3 5 1 6 4];\r\nassert(isequal(whichperm(x),y_correct))\r\n%%\r\nx = 2015;\r\ny_correct = [4 6 5 3 7];\r\nassert(isequal(whichperm(x),y_correct))\r\n%%\r\nx = 2016;\r\ny_correct = [4 6 5 3 7 2];\r\nassert(isequal(whichperm(x),y_correct))\r\n%%\r\nx = 1234567890;\r\ny_correct = [11 7 3 5 6 12 4 2 8 10 13 9];\r\nassert(isequal(whichperm(x),y_correct))\r\n%%\r\nx = 720;\r\ny_correct = [6 5 4 3 2];\r\nassert(isequal(whichperm(x),y_correct))\r\n%%\r\nx = 721;\r\ny_correct = [1 2 3 4 5 7];\r\nassert(isequal(whichperm(x),y_correct))\r\n%%\r\nx = 13;\r\ny_correct = [1 4];\r\nassert(isequal(whichperm(x),y_correct))\r\n%%\r\nx = 100;\r\ny_correct = [5 2 3];\r\nassert(isequal(whichperm(x),y_correct))\r\n%%\r\nx = 100000000;\r\ny_correct = [6 2 4 9 10 11 3 5 7 12 8];\r\nassert(isequal(whichperm(x),y_correct))\r\n%%\r\nx = 439084801;\r\ny_correct = [12];\r\nassert(isequal(whichperm(x),y_correct))\r\n%%\r\nx = flintmax;\r\ny_correct = [15 12 11 2 1 10 9 4 16 5 18 3 17 14 8 6 7 19];\r\nassert(isequal(whichperm(x),y_correct))","published":true,"deleted":false,"likes_count":2,"comments_count":0,"created_by":14358,"edited_by":null,"edited_at":null,"deleted_by":null,"deleted_at":null,"solvers_count":36,"test_suite_updated_at":"2015-08-07T10:02:05.000Z","rescore_all_solutions":true,"group_id":1,"created_at":"2015-08-06T12:28:43.000Z","updated_at":"2026-03-18T21:50:47.000Z","published_at":"2015-08-06T12:28:43.000Z","restored_at":null,"restored_by":null,"spam":false,"simulink":false,"admin_reviewed":false,"description_opc":"{\"relationships\":[{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/document\",\"targetMode\":\"\",\"relationshipId\":\"rId1\",\"target\":\"/matlab/document.xml\"},{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/output\",\"targetMode\":\"\",\"relationshipId\":\"rId2\",\"target\":\"/matlab/output.xml\"}],\"parts\":[{\"partUri\":\"/matlab/document.xml\",\"relationship\":[],\"contentType\":\"application/vnd.mathworks.matlab.code.document+xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\"?\u003e\\n\u003cw:document xmlns:w=\\\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\\\"\u003e\u003cw:body\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eLet write some permutations of positive integers.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"code\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e\u003c![CDATA[    1:    1 2 3 4 5 6 ...\\n    2:    2 1 3 4 ...\\n    3:    1 3 2 4 ...\\n    4:    2 3 1 4 ...\\n    5:    3 1 2 4 ...\\n    6:    3 2 1 4 ...\\n   25:    1 2 3 5 4 ...\\n  120:    5 4 3 2 1 6 7 ...]]\u003e\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eGiven an index, find appropriate permutation and truncate sorted part on the right side.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eexample:\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"code\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e\u003c![CDATA[323:    3 5 1 6 4 2 7 8 9 10 ...\\n\\n\u003e\u003e n = 323;\\n\u003e\u003e whichperm(n)\\nans = \\n       3 5 1 6 4]]\u003e\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eSee also:\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:hyperlink 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