Question

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[] count = new int[128];
        Arrays.fill(count, 0);

        for(int i = 0; i < magazine.length(); i++)
            count[magazine.charAt(i)]++;
        for(int i = 0; i < ransomNote.length(); i++)
            if(--count[ransomNote.charAt(i)] < 0)
                return false;

        return true;
    }
}