LeetCode 383. Ransom Note 原创Java参考解答
问题描述
https://leetcode.com/problems/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
解题思路
题目是问字符串ransomNote是否是字符串magazine中的一部分。
首先，如果ransomNote字符串长度大于magazine的字符串长度，显然不是。
接着，用一个长度26的数组统计magazine中出现的字符次数。然后用数组中的数字与ransomNote中的字符一一相减的方法，比对ransomNote中是否存在任何字符的出现次数是超出了magazine中的出现次数。
参考代码
public class Solution {
public boolean canConstruct(String ransomNote, String magazine) {
if (ransomNote.length() > magazine.length()) {
return false;
}
int[] letters = new int[26];
for (int i = 0; i < magazine.length(); i++) {
letters[magazine.charAt(i) - 'a']++;
}
for (int i = 0; i < ransomNote.length(); i++) {
letters[ransomNote.charAt(i) - 'a']--;
if (letters[ransomNote.charAt(i) - 'a'] < 0) {
return false;
}
}
return true;
}
}