383. Ransom Note [LeetCode]

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

题意：给定两个字符串，ransomNote和magazine，请判断ransomNote能否由magazine中的某些字符排列组合而成。假定所有的字符均为小写字母。

思路：显然，统计字符的出现次数即可。由于所有的字符均为小写字母，可以定义一个26元素的零数组。遍历字符串magazine，每读到一个字符，就将数组对应位置元素+1；再遍历ransomNote字符串，每读到一个字符，就将对应位置元素-1。最后遍历数组，如果存在负数元素，即返回false，否则返回true。

具体的java代码实现如下：

public class Solution {
    public boolean canConstruct(String ransomNote, String magazine) {
        int len1, len2;
        len1 = ransomNote.length();
        len2 = magazine.length();
        int count[] = new int[26];
        for (int i=0; i<26; i++)    count[i] = 0;
        for (int i=0; i