Leetcode——383. Ransom Note

题目原址

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

题目描述

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

解题思路

判断magazine中是否有ransomNote中的元素，magazine中一个元素只能使用一次。因此可以使用数组来存储字符串中的数据，同一个字符存储在同一个地址中，字符值作为数组下标，字符个数作为数组值

AC代码

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

for(int i = 0; i< ransomNote.length(); i++) {
if((--a[ransomNote.charAt(i) - 'a'] ) < 0)
return false;
}
return true;
}
}

感谢

https://leetcode.com/problems/ransom-note/discuss/85783/Java-O(n)-Solution-Easy-to-understand