242. Valid Anagram

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?

一刷
题解：统计character频率即可。

public class Solution {
    public boolean isAnagram(String s, String t) {
        int[] alphabet = new int[26];
        for (int i = 0; i < s.length(); i++) alphabet[s.charAt(i) - 'a']++;
        for (int i = 0; i < t.length(); i++) alphabet[t.charAt(i) - 'a']--;
        for (int i : alphabet) if (i != 0) return false;
        return true;
    }
}

拓展：如果为unicode，可以先将字符串sort之后再比较两个字符串是否相等

二刷
词频统计

public class Solution {
    public boolean isAnagram(String s, String t) {
        int[] freq = new int[26];
        for(int i=0; i<s.length(); i++) freq[s.charAt(i) - 'a']++;
        for(int j=0; j<t.length(); j++){
            freq[t.charAt(j) - 'a']--;
            if(freq[t.charAt(j) - 'a']<0) return false;
        }
        for(int f : freq){
            if(f!=0) return false;
        }
        return true;
    }
}