1. Problem 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

 

给出两个字符串，判断第一个字符串能否由第二个字符串构成，每个字符只能使用一次，假设都是小写。

 

2. My solution（24ms）

class Solution { public: bool canConstruct(string ransomNote, string magazine) { int cnt[26]; for(int i=0;i<26;i++) cnt[i]=0; int lenr=ransomNote.length(),lenm=magazine.length(); for(int i=0;i<lenm;i++) { int tmp=magazine[i]-'a'; cnt[tmp]++; } for(int i=0;i<lenr;i++) { int tmp=ransomNote[i]-'a'; cnt[tmp]--; if(cnt[tmp]<0) return false; } return true; } };