最大矩形面积

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题目描述

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解题思路

运用单调递增栈即可求解。

代码

#include <iostream>
#include <stack>
using namespace std;
#define MAX 100000
long long arr[MAX + 5], l[MAX + 5], r[MAX + 5];
int main()
{
    int n;
    stack<int> s;
    long long ans = 0;
    cin >> n;
    arr[0] = arr[n + 1] = -1;
    for (int i = 1; i <= n; i++)
        cin >> arr[i];
    s.push(0);
    for (int i = 1; i <= n; i++)
    {
        while (arr[s.top()] >= arr[i])
            s.pop();
        l[i] = i - s.top();
        s.push(i);
    }
    while (!s.empty())
        s.pop();
    s.push(n + 1);
    for (int i = n; i >= 1; i--)
    {
        while (arr[s.top()] >= arr[i])
            s.pop();
        r[i] = s.top() - i;
        s.push(i);
    }
    for (int i = 1; i <= n; i++)
        ans = max(ans, arr[i] * (r[i] + l[i] - 1));
    cout << ans << endl;
    return 0;
}