摘要： leetcode上关于permutation有如下几题Permutation SequenceNext PermutationPermutationsPermutations II 阅读全文

摘要： Give a string, which only contains a-z. List all the permutation of upcase and lowcase.For example, str = "ab", the output should be"ab", "aB", "Ab", "AB"for str = "abc", the output should be"abc", "abC", "aBc" 阅读全文