Lintcode: Two Strings Are Anagrams

Write a method anagram(s,t) to decide if two strings are anagrams or not.

Example
Given s="abcd", t="dcab", return true

O(N)time, O(1) space

public class Solution {
    /**
     * @param s: The first string
     * @param b: The second string
     * @return true or false
     */
    public boolean anagram(String s, String t) {
        // write your code here
        if (s==null || t==null || s.length()!=t.length()) return false;
        int[] ss = new int[256];
        int[] tt = new int[256];
        for (int i=0; i<s.length(); i++) {
            ss[s.charAt(i)]++;
            tt[t.charAt(i)]++;
        }
        for (int j=0; j<256; j++) {
            if (ss[j] != tt[j]) return false;
        }
        return true;
    }
};