383. Ransom Note

题目来源【Leetcode】

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

这道题利用a-z的ascii值作为数组下标进行存储，magazine每有一个则+1，然后ransomNote的每有一个则开始-1，如果出现负数，则不满足；

class Solution {
public:
bool canConstruct(string ransomNote, string magazine) {
int a[200];
memset(a,0,sizeof(a));
for(int i = 0; i < magazine.length(); i++){
int t = magazine[i];
a[t]++;
}
for(int i = 0; i < ransomNote.length(); i++){
int t = ransomNote[i];
a[t]--;
if(a[t] < 0) return false;
}
return true;
}
};