LeetCode Ransom Note

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

问能否从magazine字符串中抽取一些字母组成新的ransomNote字符串。简单题,直接hash解决,使用的是unordered_map,完整代码如下:

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

本代码提交AC,用时76MS。

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