84. 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.

The largest rectangle is shown in the shaded area, which has area =10
unit.
The largest rectangle is shown in the shaded area, which has area =10
unit.
For example,Given heights =[2,1,5,6,2,3],return10.

class Solution {
public:
    int largestRectangleArea(vector<int>& heights) {
        stack<int> s;
        heights.push_back(0);
        int result = 0;
        for(int i=0;i<heights.size();)
        {
            if(s.empty()||heights[i]>heights[s.top()])
                s.push(i++);
            else
              {
                  int temp = s.top();
                  s.pop();
                  result = max(result,heights[temp]*(s.empty() ? i:i-s.top()-1));
              }
        }
        return result;
    }
};