LeetCode（383）Ransom Note

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本文介绍了一个函数，用于判断是否能从给定的杂志字符串中构造出勒索信字符串。通过对每个字符计数，确保杂志字符串中的字符足够用于构建勒索信。

题目

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

判断能否由字符串magazine中的字符构造出ransom单词。

代码

#include <iostream>
#include <cstdlib>
#include <string>
#include <vector>

using namespace std;

class Solution {
public:
	bool canConstruct(string ransomNote, string magazine) {
		int rL = ransomNote.length(), mL = magazine.length();

		vector<int> v(256, 0);
		for (int i = 0; i < mL; ++i)
		{
			++v[magazine[i]];
		}//for

		for (int i = 0; i < rL; ++i)
		{
			--v[ransomNote[i]];

			if (v[ransomNote[i]] < 0)
				return false;
		}//for

		return true;
	}
};

int main()
{
	cout << Solution().canConstruct("a", "b") << endl;

	system("pause");

	return 0;
}