Given a string S, we can transform every letter individually to be lowercase or uppercase to create another string. Return a list of all possible strings we could create.
Examples: Input: S = "a1b2" Output: ["a1b2", "a1B2", "A1b2", "A1B2"] Input: S = "3z4" Output: ["3z4", "3Z4"] Input: S = "12345" Output: ["12345"]
把字符串里的字母任意改为大写或小写，求能获得的所有字符。
我的解决思路是一个个遍历字符，碰到数字直接加上，碰的字母的，就把已经有的字符串复制一遍，前面一半字符串尾补加小写字母，后面一半字符串尾补加大写字母。
class Solution { public: vector<string> letterCasePermutation(string S) { vector<string> res(1); for (int i=0; i<S.length(); ++i) { char c = S[i]; int len = res.size(); if ((c>=‘a‘ && c <=‘z‘) || (c>=‘A‘ && c<=‘Z‘)) { for (int j=0; j<len; ++j) { res.push_back(res[j]); res[j].push_back(tolower(c)); res[j+len].push_back(toupper(c)); } } else for (int j=0; j<len; ++j) res[j].push_back(c); } return res; } };