{"group":{"id":1,"name":"Community","lockable":false,"created_at":"2012-01-18T18:02:15.000Z","updated_at":"2026-05-26T00:16:20.000Z","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":"2026-05-26T00:00:00.000Z","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":1038,"title":"Change the sign of even index entries of the reversed vector","description":"change the signs of the even index entries of the reversed vector\r\n\r\nexample 1\r\nvec = [4 -1 -2 9]\r\nans = [9 2 -1 -4]\r\n\r\nexample2\r\nvec = [-4 -1 -2 -9]\r\nans = [-9 2 -1 4]","description_html":"\u003cp\u003echange the signs of the even index entries of the reversed vector\u003c/p\u003e\u003cp\u003eexample 1\r\nvec = [4 -1 -2 9]\r\nans = [9 2 -1 -4]\u003c/p\u003e\u003cp\u003eexample2\r\nvec = [-4 -1 -2 -9]\r\nans = [-9 2 -1 4]\u003c/p\u003e","function_template":"function y = your_fcn_name(x)\r\n  y = x;\r\nend","test_suite":"%%\r\nx = [4 -5 -2 9];\r\ny_correct = [9  2 -5 -4];\r\nassert(isequal(your_fcn_name(x),y_correct))\r\n\r\n%%\r\nx = ones(1,4);\r\ny_correct = [1 -1 1 -1];\r\nassert(isequal(your_fcn_name(x),y_correct))\r\n\r\n%%\r\nx = 1:10;\r\ny_correct = [10 -9 8 -7 6 -5 4 -3 2 -1];\r\nassert(isequal(your_fcn_name(x),y_correct))\r\n\r\n%%\r\nx = 2:2:12;\r\ny_correct = [12 -10 8 -6 4 -2];\r\nassert(isequal(your_fcn_name(x),y_correct))\r\n\r\n%%\r\nx = -3:3;\r\ny_correct = [3 -2 1 0 -1 2 -3];\r\nassert(isequal(your_fcn_name(x),y_correct))\r\n\r\n%%\r\nx = [1 1 2 3 5 8 13 21 34 55 89 144];\r\ny_correct = [144 -89 55 -34 21 -13 8 -5 3 -2 1 -1];\r\nassert(isequal(your_fcn_name(x),y_correct))\r\n\r\n%%\r\nx = [1 0 1 0 1 0 1 0 1 0 1 0];\r\ny_correct = [0 -1 0 -1 0 -1 0 -1 0 -1 0 -1];\r\nassert(isequal(your_fcn_name(x),y_correct))\r\n\r\n%%\r\nx = [0 1 0 2 0 3 0 4 0 5 0 6];\r\ny_correct = [6 0 5 0 4 0 3 0 2 0 1 0];\r\nassert(isequal(your_fcn_name(x),y_correct))\r\n\r\n%%\r\nx = [0 1 0 1 0 1 0 1 0 1 0 1];\r\ny_correct = [x(2:end) x(1)];\r\nassert(isequal(your_fcn_name(x),y_correct))","published":true,"deleted":false,"likes_count":5,"comments_count":1,"created_by":1023,"edited_by":null,"edited_at":null,"deleted_by":null,"deleted_at":null,"solvers_count":654,"test_suite_updated_at":"2016-11-18T03:05:04.000Z","rescore_all_solutions":false,"group_id":13,"created_at":"2012-11-19T03:18:07.000Z","updated_at":"2026-05-22T11:57:38.000Z","published_at":"2012-11-19T03:18:34.000Z","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\",\"relationshipId\":\"rId1\",\"target\":\"/matlab/document.xml\"},{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/output\",\"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\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\u003echange the signs of the even index entries of the reversed vector\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003cw:jc w:val=\\\"left\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eexample 1 vec = [4 -1 -2 9] ans = [9 2 -1 -4]\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003cw:jc w:val=\\\"left\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eexample2 vec = [-4 -1 -2 -9] ans = [-9 2 -1 4]\u003c/w:t\u003e\u003c/w:r\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":{"problems":[{"id":1038,"title":"Change the sign of even index entries of the reversed vector","description":"change the signs of the even index entries of the reversed vector\r\n\r\nexample 1\r\nvec = [4 -1 -2 9]\r\nans = [9 2 -1 -4]\r\n\r\nexample2\r\nvec = [-4 -1 -2 -9]\r\nans = [-9 2 -1 4]","description_html":"\u003cp\u003echange the signs of the even index entries of the reversed vector\u003c/p\u003e\u003cp\u003eexample 1\r\nvec = [4 -1 -2 9]\r\nans = [9 2 -1 -4]\u003c/p\u003e\u003cp\u003eexample2\r\nvec = [-4 -1 -2 -9]\r\nans = [-9 2 -1 4]\u003c/p\u003e","function_template":"function y = your_fcn_name(x)\r\n  y = x;\r\nend","test_suite":"%%\r\nx = [4 -5 -2 9];\r\ny_correct = [9  2 -5 -4];\r\nassert(isequal(your_fcn_name(x),y_correct))\r\n\r\n%%\r\nx = ones(1,4);\r\ny_correct = [1 -1 1 -1];\r\nassert(isequal(your_fcn_name(x),y_correct))\r\n\r\n%%\r\nx = 1:10;\r\ny_correct = [10 -9 8 -7 6 -5 4 -3 2 -1];\r\nassert(isequal(your_fcn_name(x),y_correct))\r\n\r\n%%\r\nx = 2:2:12;\r\ny_correct = [12 -10 8 -6 4 -2];\r\nassert(isequal(your_fcn_name(x),y_correct))\r\n\r\n%%\r\nx = -3:3;\r\ny_correct = [3 -2 1 0 -1 2 -3];\r\nassert(isequal(your_fcn_name(x),y_correct))\r\n\r\n%%\r\nx = [1 1 2 3 5 8 13 21 34 55 89 144];\r\ny_correct = [144 -89 55 -34 21 -13 8 -5 3 -2 1 -1];\r\nassert(isequal(your_fcn_name(x),y_correct))\r\n\r\n%%\r\nx = [1 0 1 0 1 0 1 0 1 0 1 0];\r\ny_correct = [0 -1 0 -1 0 -1 0 -1 0 -1 0 -1];\r\nassert(isequal(your_fcn_name(x),y_correct))\r\n\r\n%%\r\nx = [0 1 0 2 0 3 0 4 0 5 0 6];\r\ny_correct = [6 0 5 0 4 0 3 0 2 0 1 0];\r\nassert(isequal(your_fcn_name(x),y_correct))\r\n\r\n%%\r\nx = [0 1 0 1 0 1 0 1 0 1 0 1];\r\ny_correct = [x(2:end) x(1)];\r\nassert(isequal(your_fcn_name(x),y_correct))","published":true,"deleted":false,"likes_count":5,"comments_count":1,"created_by":1023,"edited_by":null,"edited_at":null,"deleted_by":null,"deleted_at":null,"solvers_count":654,"test_suite_updated_at":"2016-11-18T03:05:04.000Z","rescore_all_solutions":false,"group_id":13,"created_at":"2012-11-19T03:18:07.000Z","updated_at":"2026-05-22T11:57:38.000Z","published_at":"2012-11-19T03:18:34.000Z","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\",\"relationshipId\":\"rId1\",\"target\":\"/matlab/document.xml\"},{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/output\",\"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\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\u003echange the signs of the even index entries of the reversed vector\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003cw:jc w:val=\\\"left\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eexample 1 vec = [4 -1 -2 9] ans = [9 2 -1 -4]\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003cw:jc w:val=\\\"left\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eexample2 vec = [-4 -1 -2 -9] ans = [-9 2 -1 4]\u003c/w:t\u003e\u003c/w:r\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\"}]}"}],"errors":[],"facets":[[{"value":"Indexing II","count":1,"selected":false}],[{"value":"medium","count":1,"selected":false}]],"term":"tag:\"qmf\"","page":1,"per_page":50,"sort":"map(difficulty_value,0,0,999) asc"}}