383. 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.

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

       
       
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思路：
这是LeetCode Discuss中的最热代码，它的原理就是列出了magazine的字母表，然后算出了出现个数，然后遍历ransomNote，保证有足够的字母可用，代码非常清晰。

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       class Solution {
       
       
    public boolean canConstruct(String ransomNote, String magazine) {
       
       
        int[] arr = new int[26];
       
       
        for (int i = 0; i < magazine.length(); i++) {
       
       
            arr[magazine.charAt(i) - 'a']++;
       
       
        }
       
       
        for (int i = 0; i < ransomNote.length(); i++) {
       
       
            if(--arr[ransomNote.charAt(i)-'a'] < 0) {
       
       
                return false;
       
       
            }
       
       
        }
       
       
        return true;
       
       
    }
       
       
}
      
      
      
      

       
       
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