[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.

Note:
You may assume that both strings contain only lowercase letters.

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

Solution

class Solution {
    public boolean canConstruct(String ransomNote, String magazine) {
        int[] note = new int[26];
        for (char ch: magazine.toCharArray()) {
            note[ch-`a`]++;
        }
        for (char ch: ransomNote.toCharArray()) {
            if (--note[ch-`a`] < 0) return false; 
        }
        return true;
    }
}