【DP求最大子矩陣面積】hdu 1506

求最大子矩陣面積其實就是求每個數左邊>=a[i]的下標，右邊>=a[i]的下標，然後就會求出面積了！

#include <list>
#include <map>
#include <set>
#include <queue>
#include <string>
#include <deque>
#include <stack>
#include <algorithm>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <limits.h>
#include <time.h>
#include <string.h>
using namespace std;

#define LL long long
#define PI acos(-1.0)
#define Max INT_MAX
#define Min INT_MIN
#define eps 1e-8
#define FRE freopen("a.txt","r",stdin)
#define N 100010
LL max(LL a,LL b){return a>b?a:b;}
LL h[N];
int l[N],r[N];
int main(){
    int n;
    while(scanf("%d",&n) &&n){
        int i,j;
        for(i=1;i<=n;i++){
            scanf("%I64d",&h[i]);
            l[i]=r[i]=i;                //初始化爲i
        }
        h[0]=h[n+1]=-1;                //防止死循環！
        for(i=1;i<=n;++i)              //1~n
            while(h[l[i]-1] >= h[i])
                l[i] = l[l[i]-1];
        for(i=n;i>=1;--i)              //n~1
            while( h[r[i]+1] >= h[i])
                r[i] = r[r[i]+1];
        LL ans=0;
        for(i=1;i<=n;i++){
            ans=max(ans , (r[i]-l[i]+1)*h[i]);
        }
        printf("%I64d\n",ans);
    }
    return 0;
}