Valid Anagram

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?

class Solution {
    func isAnagram(_ s: String, _ t: String) -> Bool {
        if s.count != t.count {
            return false
        }
        
        var charCount: [Character: Int] = [:]
        for c in s {
            charCount[c, default: 0] += 1
        }
        
        for c in t {
            charCount[c, default: 0] -= 1
            
            if charCount[c, default: 0] < 0 {
                return false
            }
        }
        
        return true
    }
}

public class Solution {
    public boolean isAnagram(String s, String t) {
        if (s == null || t == null) {
            return false;
        }
        
        if (s.length() != t.length()) {
            return false;
        }
        
        int[] charCount = new int[256];
        for (int i = 0; i < s.length(); i++) {
            charCount[s.charAt(i)]++;
        }
        
        for (int i = 0; i < t.length(); i++) {
            if (--charCount[t.charAt(i)] < 0) {
                return false;
            }
        }

        return true;
    }
}

Hope this helps,
Michael