leetcode

0 class Solution {

1 static const int MOD = 1e9 + 7;

2

3 public:

4 int sumSubarrayMins(const vector<int> &arr) {

5 const int n = arr.size();

6 stack<int> st;

7

8 long long res = 0;

9 for (int right = 0, mid, left; right <= n; right++) {

10 while (!st.empty() && (right == n || arr[st.top()] > arr[right])) {

11 mid = st.top(), st.pop();

12 left = st.empty() ? -1 : st.top();

13 res = (res + (long long)arr[mid] * (right - mid) * (mid - left)) % MOD;

14 }

15 st.push(right);

16 }

17 return res;

18 }

19 };