1 int main() {
2 vector<int> nums{ 5,4,2,6,7,3,9 };
3 int length = nums.size();
4
5 stack<vector<int>>sk1;
6 vector<int>rightFirstMax(length, 0);
7 for (int index = length - 1; index >= 0; index--) {
8 while (!sk1.empty() && nums[index] > sk1.top()[0]) {
9 sk1.pop();
10 }
11 if (!sk1.empty()) {
12 rightFirstMax[index] = sk1.top()[1];
13 }
14 vector<int>temp(2, 0);
15 temp[0] = nums[index];
16 temp[1] = index;
17 sk1.push(temp);
18 }
19
20 vector<int>leftFirstMin(length, 0);
21 stack<vector<int>>sk2;
22 for (int index = 0; index < length; index++) {
23 while (!sk2.empty() && nums[index] < sk2.top()[0]) {
24 sk2.pop();
25 }
26 if (!sk2.empty()) {
27 leftFirstMin[index] = sk2.top()[1];
28 }
29 vector<int>temp(2, 0);
30 temp[0] = nums[index];
31 temp[1] = index;
32 sk2.push(temp);
33 }
34
35 int res = 0;
36 for (int i = 0; i < length; ++i) {
37 int temp = rightFirstMax[i] * leftFirstMin[i];
38 if (temp > res) {
39 res = temp;
40 }
41 }
42 cout << res;
43 return 0;
44 }
