LeetCode 383 Ransom Note

Problem:

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.

You may assume that both strings contain only lowercase letters.

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

Summary:

给出两个字符串r，m，判断r串能否由m串组成。即r串中的所有字母包含在m串中即可。

Analysis:

Hash表

 1 class Solution {
 2 public:
 3     bool canConstruct(string ransomNote, string magazine) {
 4         int magChar[26] = {0};
 5         int len = magazine.size();
 6         for (int i = 0; i < len; i++) {
 7             magChar[magazine[i] - 'a']++;
 8         }
 9         
10         len = ransomNote.size();
11         for (int i = 0; i < len; i++) {
12             if (--magChar[ransomNote[i] - 'a'] < 0) {
13                 return false;
14             }
15         }
16         
17         return true;
18     }
19 };