POJ - 2559 Largest Rectangle in a Histogram 单调栈

#include <algorithm>
#include <iostream>
#include <sstream>
#include <cstring>
#include <cstdlib>
#include <string>
#include <vector>
#include <cstdio>
#include <cmath>
#include <queue>
#include <stack>
#include <map>
#include <set>
using namespace std;

int l[100005],r[100005],h1[100005];
long long max1,p;

int main()
{
int n;
while (scanf("%d",&n)!=EOF&&n)
{
for (int i=1; i<=n; i++)
{
scanf("%d",&h1[i]);
}
h1[0]=-1;
for (int i=1; i<=n; i++)
{
int j=i-1;
while (h1[i]<=h1[j]) j=l[j];
l[i]=j;
}
h1[n+1]=-1;
for (int i=n; i>0; i--)
{
int j=i+1;
while (h1[i]<=h1[j]) j=r[j];
r[i]=j;
}
max1=0;
for (int i=1; i<=n; i++)
{
p=(long long)(r[i]-l[i]-1)*h1[i];
max1=p>max1?p:max1;
}
cout<<max1<<endl;
}
return 0;
}