pku2559_Largest Rectangle in a Histogram

http://poj.org/problem?id=2559

类似pku2796，求出每个数的区间再计算得出要求的那个最大值。。。

01 #include <cstdio>
02 #include <algorithm>
03 using namespace std;
04
05 const int N = 100000 + 10;
06 long long h [N ];
07 int l [N ], r [N ], stack [N ];
08
09 int main()
10 {
11     int n;
12     while ( scanf( "%d" , &n) != EOF && n)
13     {
14         for ( int i = 1; i <= n; i ++)
15             scanf( "%lld" , & h [ i ]);
16         //求左边界
17         int top = 0;
18         stack [ top ] = 0;
19         h [ 0 ] = - 1;
20         for ( int i = 1; i <= n; i ++)
21         {
22             while ( h [ stack [ top ]] >= h [ i ])
23                 top --;
24             l [ i ] = stack [ top ] + 1;
25             stack [ ++ top ] = i;;
26         }
27         //求右边界
28         top = 0;
29         stack [ top ] = n + 1;
30         h [n + 1 ] = - 1;
31         for ( int i = n; i >= 1; i --)
32         {
33             while ( h [ stack [ top ]] >= h [ i ])
34                 top --;
35             r [ i ] = stack [ top ] - 1;
36             stack [ ++ top ] = i;
37         }
38         long long ans = - 1;
39         for ( int i = 1; i <= n; i ++)
40             ans = max( ans , ( r [ i ] - l [ i ] + 1) * h [ i ]);
41         printf( "%lld \n " , ans);
42     }
43 }