leetcode 383. Ransom Note

383. Ransom Note

Given an arbitrary ransom note string and another string containing letters from all the magazines, write a function that will return true if the ransom note can be constructed from the magazines ; otherwise, it will return false. 

Each letter in the magazine string can only be used once in your ransom note.

Note:
You may assume that both strings contain only lowercase letters.

canConstruct("a", "b") -> falsecanConstruct("aa", "ab") -> falsecanConstruct("aa", "aab") -> true

简单map

class Solution {public:    bool canConstruct(string ransomNote, string magazine)     {        map<char, int> mp;        for (int i = 0; i< magazine.size(); i++)        {            mp[magazine[i]] ++;           }        for (int i = 0; i< ransomNote.size(); i++)        {            if (mp.find(ransomNote[i]) == mp.end()) return false;            else if ( --mp[ransomNote[i]] == 0)    mp.erase(ransomNote[i]);        }        return true;    }};