#Leetcode# 917. Reverse Only Letters

https://leetcode.com/problems/reverse-only-letters/

Given a string S, return the "reversed" string where all characters that are not a letter stay in the same place, and all letters reverse their positions.

 

Example 1:

Input: "ab-cd"
Output: "dc-ba"

Example 2:

Input: "a-bC-dEf-ghIj"
Output: "j-Ih-gfE-dCba"

Example 3:

Input: "Test1ng-Leet=code-Q!"
Output: "Qedo1ct-eeLg=ntse-T!"

Note:

1. S.length <= 100
2. 33 <= S[i].ASCIIcode <= 122
3. S doesn't contain \ or "

代码：

class Solution {
public:
    string reverseOnlyLetters(string S) {
        string ans = "";
        vector<char> v;
        int len = S.length();
        for(int i = len - 1; i >= 0; i --) {
            if(S[i] >= 'a' && S[i] <= 'z' || S[i] >= 'A' && S[i] <= 'Z')
                v.push_back(S[i]);
        }

        int rec = 0;
        for(int i = 0; i < len; i ++) {
            if(S[i] >= 'a' && S[i] <= 'z' || S[i] >= 'A' && S[i] <= 'Z') {
                char c = v[rec];
                ans += c;
                rec ++;
            }
            else ans += S[i];
        }

        return ans;
    }
};