HDU 1506 Largest Rectangle in a Histogram （dp左右处理边界的矩形问题）

#include<stdio.h>
#include<string.h>
#include<iostream>
#include<algorithm>
using namespace std;
const int maxn=100005;
typedef long long int ll;
ll l[maxn],r[maxn],h[maxn];
int main(){
    int n;
    while(scanf("%d",&n)!=EOF){
        if(!n)
        break;
        memset(l,0,sizeof(l));
        memset(r,0,sizeof(r));
        memset(h,0,sizeof(h));
  //          memset(dp,0,sizeof(dp));
        for(int i=1;i<=n;i++){
           scanf("%lld",&h[i]);

        }
        l[1]=1;
        r[n]=n;

        for(int i=2;i<=n;i++){
             int tmp=i;
            while(tmp>1&&h[i]<=h[tmp-1])
            tmp=l[tmp-1];

            l[i]=tmp;
        }

        for(int i=n-1;i>=1;i--){
              int tmp=i;
            while(tmp<n&&h[i]<=h[tmp+1])
            tmp=r[tmp+1];
            r[i]=tmp;
        }
        ll ans=-1;
        for(int i=1;i<=n;i++){
           ll tmp=(r[i]-l[i]+1)*h[i];
            ans=max(ans,tmp);
        }
      printf("%lld\n",ans);
    }
    return 0;
}