[leetcode-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.

思路：

anagram有一个特点就是排序之后，字符串是相等的。

bool isAnagram(string s, string t) 
{
  if(s.size()!=t.size())return false;
  map<string,int>m;
  sort(s.begin(),s.end()); 
  sort(t.begin(),t.end());
  m[s]++;
  m[t]++;
   if(m.size()==2)return false;
   return true;  
}

还可以用hash

bool isAnagram(string s, string t) {
        if (s.length() != t.length()) return false;
        int n = s.length();
        unordered_map<char, int> counts;
        for (int i = 0; i < n; i++) {
            counts[s[i]]++;
            counts[t[i]]--;
        }
        for (auto count : counts)
            if (count.second) return false;
        return true;
    }

bool isAnagram(string s, string t) {
        if (s.length() != t.length()) return false;
        int n = s.length();
        int counts[26] = {0};
        for (int i = 0; i < n; i++) { 
            counts[s[i] - 'a']++;
            counts[t[i] - 'a']--;
        }
        for (int i = 0; i < 26; i++)
            if (counts[i]) return false;
        return true;
    }

参考：

https://discuss.leetcode.com/topic/20303/2-c-solutions-with-explanations