Description

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") -> false
canConstruct("aa", "ab") -> false
canConstruct("aa", "aab") -> true

分析

题目的意思是： 给定连个random字符串和一个magazine字符串，问random可不可以由magazine字符串组成。

  • 如果理解题意了，用一个map就可以搞定了，详情请看代码。

代码

class Solution {
public:
    bool canConstruct(string ransomNote, string magazine) {
        unordered_map<char, int> m;
        for(auto c:magazine){
            m[c]++;
        }
        for(auto c:ransomNote){
            if(--m[c]<0) return false;
        }
        return true;
    }
};

参考文献

​​[LeetCode] Ransom Note 赎金条​​