暑期训练狂刷系列——Hdu 3506 Largest Rectangle in a Histogram （单调栈）

 1 //#include <bits/stdc++.h>
 2 #include <iostream>
 3 #include <algorithm>
 4 #include <cstdio>
 5 using namespace std;
 6 const int maxn = 100005;
 7 #define LL long long//要用LL,数据范围太大，int会溢出
 8 struct node
 9 {
10     LL x, index;
11 } Stack[maxn];
12 
13 int main ()
14 {
15     LL n;
16     while (scanf ("%I64d", &n), n)
17     {
18         LL sum = 0;
19         LL head, last, num, m;
20         head = 0;
21         last = -1;
22         for (LL i=0; i<=n; i++)
23         {
24             if (i == n)//在数列后面加一个0，以便于清空栈内元素
25                 num = 0;
26             else
27                 scanf ("%I64d", &num);
28             m = i;//记录当前元素向前延伸的边界
29             while (head<=last && Stack[last].x>num)
30             {
31                 sum = max(sum, (i - Stack[last].index)*Stack[last].x);
32                 m = Stack[last].index;
33                 last --;
34             }
35             Stack[++last].index = m;
36             Stack[last].x = num;
37         }
38         printf ("%I64d\n", sum);
39     }
40     return 0;
41 }