[leetcode] 917. Reverse Only Letters : https://leetcode.com/problems/reverse-only-letters/

Reverse Only Letters.cc

class Solution {
public:
    
    bool isCharacter(char c){
        return ('a'<=c && c<='z') || ('A'<=c && c<='Z');
    }
    
    string reverseOnlyLetters(string S) {
        queue<char> q;
        stack<char> s;
        for(int i=0;i<S.size();i++){
            char now = S[i];
            if(isCharacter(now))
                s.push(now);
            else
                q.push(now);
        }
        
        string ans = "";
        for(int i=0;i<S.size();i++){
            if(isCharacter(S[i])){
                ans += s.top();
                s.pop();
            }
            else{
                ans += q.front();
                q.pop();
            }
        }
        return ans;
    }
};