【LeetCode】84. Largest Rectangle in Histogram

Largest Rectangle in Histogram

Given n non-negative integers representing the histogram's bar height where the width of each bar is 1, find the area of largest rectangle in the histogram.

 

Above is a histogram where width of each bar is 1, given height = [2,1,5,6,2,3].

 

 

The largest rectangle is shown in the shaded area, which has area = 10 unit.

 

For example,
Given height = [2,1,5,6,2,3],
return 10.

具体思路也是用stack的思想，相比其他的需要40ms以上我使用了将while循环拆分开来，从而可以将

算法的复杂度更进一步降低，运算时间为16ms

 

class Solution {
public:
int largestRectangleArea(vector<int>& height) {
if(0==height.size())
return 0;
if(1==height.size())
return height[0];
vector<int>index;
height.push_back(-1);
int count=-1;
int ans=0;
int len=height.size();
for(int i=0;i<height.size();)
{

int peak=index.size()-1;
if(-1==peak)
{
index.push_back(i);
i++;
}
while(i<len&&height[i]>=height[index[peak]])
{
index.push_back(i);
i++;
peak=index.size()-1;
}
peak=index.size()-1;
int tmp=index[peak];
while(peak>-1&&height[index[peak]]>height[i])
{

if(peak==0)
{
count=height[index[peak]]*i;
index.pop_back();
peak=index.size()-1;
}
else
{
int mm=index[peak];
index.pop_back();
peak=index.size()-1;
count=height[mm]*(i-index[peak]-1);
}
if(count>ans)
ans=count;
}
}
return ans;
}
};