leetcode

0 class Solution {

1 public:

2 int numberOfArithmeticSlices(const vector<int> &nums) const {

3 vector<unordered_map<long long, int>> dp(size(nums));

4 int res = 0;

5 for (int i = 1; i < size(nums); i++) {

6 for (int j = 0; j < i; j++) {

7 const long long diff = (long long)nums[i] - nums[j];

8 const int cnt = dp[j].count(diff) ? dp[j][diff] : 0;

9 dp[i][diff] += cnt + 1;

10 res += cnt;

11 }

12 }

13 return res;

14 }

15 };