{"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":595,"title":"Reduce - Map-Reduce","description":"Write reduce function, that takes arguments and \r\nconstantly folds results into next call argument,\r\nfinally returning a value; i.e. for a binary operator Fb,\r\n\r\n     reduce(Fb,{a,b,c},start_val) = F(F(F(start_val,a),b),c)\r\n\r\nSame can be done for a n-ary operators.\r\n\r\n\r\nEg. reduce(@strcat,{'foo','bar','baz','bat'},' ') = \r\n    reduce(@plus,{1,2,3,4},0) = 10\r\n    reduce(@max,{1,2,3,4},{5,6,7,8},5) = 8\r\n\r\nRemember, we use cell arrays for passing arguments, not matrices!","description_html":"\u003cp\u003eWrite reduce function, that takes arguments and \r\nconstantly folds results into next call argument,\r\nfinally returning a value; i.e. for a binary operator Fb,\u003c/p\u003e\u003cpre\u003e     reduce(Fb,{a,b,c},start_val) = F(F(F(start_val,a),b),c)\u003c/pre\u003e\u003cp\u003eSame can be done for a n-ary operators.\u003c/p\u003e\u003cp\u003eEg. reduce(@strcat,{'foo','bar','baz','bat'},' ') = \r\n    reduce(@plus,{1,2,3,4},0) = 10\r\n    reduce(@max,{1,2,3,4},{5,6,7,8},5) = 8\u003c/p\u003e\u003cp\u003eRemember, we use cell arrays for passing arguments, not matrices!\u003c/p\u003e","function_template":"function y = reduce(varargin)\r\n  F = varargin{1};\r\n  args = varargin{2:end-1};\r\n  start_val = varargin{end};\r\nend\r\n","test_suite":"assert(strcmp(reduce(@strcat,{'foo','bar','baz','bat'},'-'),'-foobarbazbat'))\r\nassert(reduce(@max,{1,2,3,4},{5,6,7,8},5)==8)\r\nassert(reduce(@min,{1,2,3,4},{5,6,7,8},5)==1)\r\n","published":true,"deleted":false,"likes_count":1,"comments_count":3,"created_by":3378,"edited_by":null,"edited_at":null,"deleted_by":null,"deleted_at":null,"solvers_count":20,"test_suite_updated_at":"2012-04-17T20:11:35.000Z","rescore_all_solutions":false,"group_id":1,"created_at":"2012-04-17T20:11:35.000Z","updated_at":"2026-05-26T03:33:44.000Z","published_at":"2012-04-17T20:11:35.000Z","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\u003eWrite reduce function, that takes arguments and constantly folds results into next call argument, finally returning a value; i.e. for a binary operator Fb,\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[     reduce(Fb,{a,b,c},start_val) = F(F(F(start_val,a),b),c)]]\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\u003eSame can be done for a n-ary operators.\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\u003eEg. reduce(@strcat,{'foo','bar','baz','bat'},' ') = reduce(@plus,{1,2,3,4},0) = 10 reduce(@max,{1,2,3,4},{5,6,7,8},5) = 8\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\u003eRemember, we use cell arrays for passing arguments, not matrices!\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":595,"title":"Reduce - Map-Reduce","description":"Write reduce function, that takes arguments and \r\nconstantly folds results into next call argument,\r\nfinally returning a value; i.e. for a binary operator Fb,\r\n\r\n     reduce(Fb,{a,b,c},start_val) = F(F(F(start_val,a),b),c)\r\n\r\nSame can be done for a n-ary operators.\r\n\r\n\r\nEg. reduce(@strcat,{'foo','bar','baz','bat'},' ') = \r\n    reduce(@plus,{1,2,3,4},0) = 10\r\n    reduce(@max,{1,2,3,4},{5,6,7,8},5) = 8\r\n\r\nRemember, we use cell arrays for passing arguments, not matrices!","description_html":"\u003cp\u003eWrite reduce function, that takes arguments and \r\nconstantly folds results into next call argument,\r\nfinally returning a value; i.e. for a binary operator Fb,\u003c/p\u003e\u003cpre\u003e     reduce(Fb,{a,b,c},start_val) = F(F(F(start_val,a),b),c)\u003c/pre\u003e\u003cp\u003eSame can be done for a n-ary operators.\u003c/p\u003e\u003cp\u003eEg. reduce(@strcat,{'foo','bar','baz','bat'},' ') = \r\n    reduce(@plus,{1,2,3,4},0) = 10\r\n    reduce(@max,{1,2,3,4},{5,6,7,8},5) = 8\u003c/p\u003e\u003cp\u003eRemember, we use cell arrays for passing arguments, not matrices!\u003c/p\u003e","function_template":"function y = reduce(varargin)\r\n  F = varargin{1};\r\n  args = varargin{2:end-1};\r\n  start_val = varargin{end};\r\nend\r\n","test_suite":"assert(strcmp(reduce(@strcat,{'foo','bar','baz','bat'},'-'),'-foobarbazbat'))\r\nassert(reduce(@max,{1,2,3,4},{5,6,7,8},5)==8)\r\nassert(reduce(@min,{1,2,3,4},{5,6,7,8},5)==1)\r\n","published":true,"deleted":false,"likes_count":1,"comments_count":3,"created_by":3378,"edited_by":null,"edited_at":null,"deleted_by":null,"deleted_at":null,"solvers_count":20,"test_suite_updated_at":"2012-04-17T20:11:35.000Z","rescore_all_solutions":false,"group_id":1,"created_at":"2012-04-17T20:11:35.000Z","updated_at":"2026-05-26T03:33:44.000Z","published_at":"2012-04-17T20:11:35.000Z","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\u003eWrite reduce function, that takes arguments and constantly folds results into next call argument, finally returning a value; i.e. for a binary operator Fb,\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[     reduce(Fb,{a,b,c},start_val) = F(F(F(start_val,a),b),c)]]\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\u003eSame can be done for a n-ary operators.\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\u003eEg. reduce(@strcat,{'foo','bar','baz','bat'},' ') = reduce(@plus,{1,2,3,4},0) = 10 reduce(@max,{1,2,3,4},{5,6,7,8},5) = 8\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\u003eRemember, we use cell arrays for passing arguments, not matrices!\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":"medium","count":1,"selected":false}]],"term":"tag:\"map-reduce\"","page":1,"per_page":50,"sort":"map(difficulty_value,0,0,999) asc"}}