1const sumSubarrayMins = (arr) => {
2    const MOD = 1e9 + 7;
3    const n = arr.length;
4    const stack = [];
5    let result = 0;
6
7    for (let i = 0; i <= n; i++) {
8        while (stack.length > 0 && (i === n || arr[stack[stack.length - 1]] >= arr[i])) {
9            const curIndex = stack.pop();
10            const curValue = arr[curIndex];
11            const left = stack.length > 0 ? curIndex - stack[stack.length - 1] : curIndex + 1;
12            const right = i - curIndex;
13            result = (result + curValue * left * right) % MOD;
14        }
15        stack.push(i);
16    }
17
18    return result;
19};

1#include <stack>
using namespace std;

typedef long long ll;

class Solution {
public:
    int sumSubarrayMins(vector<int>& arr) {
        int MOD = 1e9 + 7;
        int n = arr.size();
        vector<int> dp(n);
        stack<int> s;
        ll result = 0;

        for (int i = 0; i < n; ++i) {
            while (!s.empty() && arr[s.top()] >= arr[i]) s.pop();
            int k = (s.empty()) ? i + 1 : i - s.top();
            dp[i] = (arr[i] * k + (s.empty() ? 0 : dp[s.top()])) % MOD;
            result = (result + dp[i]) % MOD;
            s.push(i);
        }

        return (int)result;
    }
};