HDU 1506 Largest Rectangle in a Histogram(单调栈)

此题和POJ的feel good类似，只不过最后直接求解的是max=a[i]*(r[i]-l[i]+1);坑点是输入的n个数必须用I64,否则WA。

#include<algorithm>
#include<iostream>
#include<stdio.h>
#include<string.h>
#include<cstdio>
#include<cstdlib>
#include<string>
#include<queue>
#include<map>
#include<cmath>
#define L1 long long
#define L2 __int64
#define inf 0x3f3f3f3f
using namespace std;

L2 a[1000000];
L2 l[1000100],r[1000100];
int main()
{
int n,m,i,j,k;
while(~scanf("%d",&n)&&n)
{
for(i=1;i<=n;i++){
scanf("%I64d",&a[i]);
l[i]=r[i]=i;
}
for(i=1;i<=n;++i){
while(l[i]>1&&a[l[i]-1 ]>=a[i] ){
l[i]=l[l[i]-1 ];
}
}
for(i=n;i>=1;--i){
while(r[i]<n&&a[r[i]+1 ]>=a[i]){
r[i]=r[r[i]+1 ];
}
}

L2 ma=0;
for(i=1;i<=n;i++){
L2 t=(r[i]-l[i]+1 )*a[i];
if(t>ma){
ma=t;
}
}
printf("%I64d\n",ma);
}
return 0;
}