Largest Rectangle in a Histogram
A histogram is a polygon composed of a sequence of rectangles aligned at a common base line. The rectangles have equal widths but may have different heights. For example, the figure on the left shows the histogram that consists of rectangles with the heights 2, 1, 4, 5, 1, 3, 3, measured in units where 1 is the width of the rectangles:
Usually, histograms are used to represent discrete distributions, e.g., the frequencies of characters in texts. Note that the order of the rectangles, i.e., their heights, is important. Calculate the area of the largest rectangle in a histogram that is aligned at the common base line, too. The figure on the right shows the largest aligned rectangle for the depicted histogram.
Input
The input contains several test cases. Each test case describes a histogram and starts with an integer n, denoting the number of rectangles it is composed of. You may assume that 1 <= n <= 100000. Then follow n integers h1, ..., hn, where 0 <= hi <= 1000000000. These numbers denote the heights of the rectangles of the histogram in left-to-right order. The width of each rectangle is 1. A zero follows the input for the last test case.
Output
For each test case output on a single line the area of the largest rectangle in the specified histogram. Remember that this rectangle must be aligned at the common base line.
Sample Input
7 2 1 4 5 1 3 3 4 1000 1000 1000 1000 0
Sample Output
8 4000
这个题是一个单调栈的应用。没错我也不会做 - -。从网上找了一个，定义了一个结构体，{int val;int len}
通过不断地更新len来记录最大的面积 。
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#define INF 0x3f3f3f3f
using namespace std;
typedef long long ll;
ll high[100005],n;
struct node {
ll val; //高
ll len; // 宽
};
ll findleft()
{
stack s;
node q;
ll temp=0,m,skr=0;
for(ll i=1;i<=n;i++)
{
cin>>q.val;
q.len=1; //每一个新输入的长度均为1
temp=0;
if(s.empty()) //当栈为空时就压进去就行了
{
s.push(q);
}
else if((s.top()).val>q.val) // 不是<=
{
while(!s.empty() && (s.top()).val>q.val)
{
(s.top()).len+=temp; //temp 用来记录他左边有多少个比他大的，从而让他的宽度改
//变。
m=(s.top()).val*(s.top()).len; //面积 ；
if(skrskr)skr=m;
temp=(s.top()).len;
s.pop();
}
return skr;
}
int main()
{ long long maxSize=0;
cin>>n;
while(n!=0)
{
ll s = findleft();
cout<>n;
}
return 0;
}