string容器的insert用法

791. Custom Sort String

Medium

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​

​S​

​​ and ​

​T​

​​ are strings composed of lowercase letters. In ​

​S​

​, no letter occurs more than once.

​

​S​

​​ was sorted in some custom order previously. We want to permute the characters of ​

​T​

​​ so that they match the order that ​

​S​

​​was sorted. More specifically, if ​

​x​

​​ occurs before ​

​y​

​​ in ​

​S​

​​, then ​

​x​

​​ should occur before ​

​y​

​ in the returned string.

Return any permutation of ​

​T​

​ (as a string) that satisfies this property.

class Solution {
public:
    string customSortString(string S, string T) {
        unordered_map<char,int> _map;
        string Result = "";
        for(char c : T){
            _map[c] ++;
        }
        for(char c : S){
            if(_map[c] > 0){
                //--在Result的结尾处插入_map[c]个c
                Result.insert(Result.length(),_map[c],c);
                _map[c] = 0;
            }
        }
        for(unordered_map<char,int>::iterator it = _map.begin();it != _map.end();it++){
            if(it->first != 0){
                Result.insert(Result.length(),it->second,it->first);
            }
        }
        return Result;
    }
};