leetcode解题之 77. Combinations&78. Subsets&90. Subsets II java 版(求所有子集)
77.Combinations(求等于指定数目集合)Giventwointegersnandk,returnallpossiblecombinationsofknumbersoutof1...n.Forexample,Ifn=4andk=2,asolutionis:[[2,4],[3,4],[2,3],[1,2],[1,3],[1,4],]dfs+回溯publicList>combine(intn