hdoj - 1506 直方图中最大的矩形

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>

using namespace std;

int a[100005];
int l[100005],r[100005];
int main()
{
    int n;
    
    while(scanf("%d",&n) && n != 0)
    {
        long long ans=0;
        memset(a,0,sizeof(a));
        for(int i = 0;i<n;i++)
        {
            scanf("%d",&a[i]);
            l[i] = r[i] = i;
            while(l[i] > 0 && a[l[i]-1] >= a[i])
            {
                l[i] = l[l[i]-1];
            }
        }
        for(int i = n-1;i>=0;i--)
        {
            while(r[i]<n-1 && a[r[i]+1] >= a[i])
            {
                r[i] = r[r[i]+1];
            }
        }
        for(int i = 0;i<n;i++)
        {
            long long  s = (long long)a[i]*(r[i]-l[i]+1);
            if(s>ans)
            {
                ans = s;
            }
        }
        printf("%lld\n",ans);
    }
    return 0;
}