赎金信(C++)

输入：ransomNote = "a", magazine = "b"
输出：false

输入：ransomNote = "aa", magazine = "ab"
输出：false

输入：ransomNote = "aa", magazine = "aab"
输出：true

class Solution {
public:
    bool canConstruct(string ransomNote, string magazine) {
        // 本质上还是一个字符统计问题
        if (ransomNote.size() > magazine.size()) return false;
        vector<int> cnt(30);
        for (auto c : magazine) cnt[c - 'a'] ++;
        for (auto c : ransomNote)
        {
            cnt [c - 'a'] --;
            if (cnt[c - 'a'] < 0)  return false;
        }
        return true;
    }
};