【POJ 2559】 Largest Rectangle in a Histogram

【题目链接】

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

【算法】

单调栈

【代码】

#include <algorithm>
#include <bitset>
#include <cctype>
#include <cerrno>
#include <clocale>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <limits>
#include <list>
#include <map>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <utility>
#include <vector>
#include <cwchar>
#include <cwctype>
#include <stack>
#include <limits.h>
using namespace std;
#define MAXN 100010

int i,top,n;
long long a[MAXN],s[MAXN],w[MAXN],stk[MAXN];
long long ans,tmp;

int main()
{

        while (scanf("%d",&n) != EOF && n)
        {
                for (i = ; i <= n; i++) scanf("%lld",&a[i]);
                ans = -;
                a[++n] = -;
                s[top = ] = -;
                for (i = ; i <= n; i++)
                {
                        if (a[i] >= s[top])
                        {
                                s[++top] = a[i];
                                w[top] = ;
                        } else
                        {
                                tmp = ;
                                while (a[i] < s[top])
                                {
                                        tmp += w[top];
                                        ans = max(ans,tmp*s[top]);
                                        top--;
                                }
                                s[++top] = a[i]; w[top] = tmp + ;
                        }
                }
                printf("%lld\n",ans);
        }

        return ;

}