LeetCode-242.Valid Anagram

https://leetcode.com/problems/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?

方法1

哈希表

public bool IsAnagram(string s, string t) 
    {
        int n = s.Length;
        if (t.Length != n)
            return false;
        Hashtable table  = new Hashtable();
        for (int i = 0; i < n; i++)
        {
            if (table.Contains(s[i]))
                table[s[i]] = (int)table[s[i]] + 1;
            else
                table.Add(s[i], 1);
            if (table.Contains(t[i]))
                table[t[i]] = (int)table[t[i]] - 1;
            else
                table.Add(t[i], -1);
        }
         foreach (DictionaryEntry item in table)
        {
            if ((int)item.Value != 0)
                return false;
        }
        return true;
    }

用数组替代哈希表

public bool IsAnagram(string s, string t) 
    {
        int n = s.Length;
        if (t.Length != n)
            return false;
        int[] table = new int[26];
        for (int i = 0; i < n; i++)
        {
            table[s[i]-'a']++;
            table[t[i]-'a']--;
        }
        for (int i = 0; i < 26; i++)
        {
            if (table[i] != 0)
                return false;
        }
        return true;
    }

方法2 

排序后比较

 public bool IsAnagram(string s, string t) 
    {
        int n = s.Length;
        if (t.Length != n)
            return false;
        char[] ss = s.ToCharArray();
        char[] tt = t.ToCharArray();
        Array.Sort(ss);
        Array.Sort(tt);
        return new string(ss)==new string(tt);
    }