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.

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

Solution：

思路：
Time Complexity: O(magazine.len) Space Complexity: O(1)

Solution Code：

class Solution {
    public boolean canConstruct(String ransomNote, String magazine) {
        int[] count = new int[26];
        for (int i = 0; i < magazine.length(); i++) {
            count[magazine.charAt(i) - 'a']++;
        }
        for (int i = 0; i < ransomNote.length(); i++) {
            if(count[ransomNote.charAt(i) - 'a']-- < 1) {
                return false;
            }
        }
        return true;
    }
}