题目描述

Given two strings s and t, write a function to determine if t is an anagram of s.

For example,
s = “anagram”, t = “nagaram”, return true.
s = “rat”, t = “car”, return false.

Note:
You may assume the string contains only lowercase alphabets.

Follow up:
What if the inputs contain unicode characters? How would you adapt your solution to such case?

分析

用数组模拟哈希表，统计字符出现次数。

–

代码

    public boolean isAnagram(String s, String t) {

        if (s == null || t == null) {
            return false;
        }

        if (s.length() != t.length()) {
            return false;
        }

        if (s.equals(t)) {
            return false;
        }

        int len = s.length();
        int[] map = new int[26];

        // 统计s中每个字符出现的次数
        for (int i = 0; i < len; i++) {
            map[s.charAt(i) - 'a']++;
        }

        // 减去t中相应字符出现次数
        for (int i = 0; i < len; i++) {
            map[t.charAt(i) - 'a']--;
            if (map[t.charAt(i) - 'a'] < 0) {
                return false;
            }
        }

        for (int i = 0; i < 26; i++) {
            if (map[i] != 0) {
                return false;
            }
        }

        return true;
    }