leetcode

0 class Solution {

1 public:

2 int numOfPairs(const vector<string> &nums, const string target) {

3 unordered_map<string, int> um;

4 for (const auto &s : nums)

5 um[s]++;

6

7 int res = 0;

8 for (int i = 0; i < target.size(); i++) {

9 const string s1 = target.substr(0, i);

10 const string s2 = target.substr(i);

11 res += (s1 != s2) ? um[s1] * um[s2] : um[s1] * (um[s1] - 1);

12 }

13 return res;

14 }

15 };