Sherlock and Anagrams

• Time : O(n^2)
• Space : O(n)

int helper(string& s, int len) {
     int res = 0, n = s.length();
     unordered_map<string, int> freq;
     for(int i = 0; i <= n - len; i++) {
         string sub = s.substr(i, len);
         sort(begin(sub), end(sub));
         res += freq[sub];
         freq[sub]++;
     }
     return res;
 }

int sherlockAndAnagrams(string s) {
    int res = 0, n = s.length();
    for(int i = 1; i < n; i++) {
        res += helper(s, i);
    }
    return res;
}