383. 赎金信

哈希表

class Solution {
    public boolean canConstruct(String ransomNote, String magazine) {

        int[] arr = new int[128];

        for (int i = 0; i < magazine.length(); i++) {
            arr[magazine.charAt(i)]++;
        }

        for (int i = 0; i < ransomNote.length(); i++) {

            int num = arr[ransomNote.charAt(i)];

            if (num > 0){
                arr[ransomNote.charAt(i)]--;
            }
            else {
                return false;
            }
        }
        
        return true;
    }
}

/**
 * 时间复杂度 O(n)
 * 空间复杂度 O(1)
 */

https://leetcode-cn.com/problems/ransom-note/