Custom Sort String (Leetcode 791

A家的题。

解法1直接sort,

class Solution {
public:
    string customSortString(string S, string T) {
        if(S.empty()){
            return T;
        }
        
        auto comp = [&S](const char c1, const char c2){
            return S.find(c1) < S.find(c2);
        };
        
        sort(T.begin(), T.end(), comp);
        return T;
    }
};

解法二：记下string T中每个char的个数，然后再loop S, 按照S的顺序recover出来

class Solution {
public:
string customSortString(string S, string T) {
unordered_map<char, int> mp;
for(char c : T){
mp[c]++;
}

    string ret = "";
    
    for(char c : S){
        if(mp.count(c)){
            int cnt = mp[c];
            ret += string(cnt, c);
            mp.erase(c);
        }
        
    }
    
    for(auto it : mp){
        char c = it.first; int cnt = it.second;
        ret += string(cnt, c);
    }
    
    return ret;
}

};