LeetCode 84. Largest Rectangle in Histogram

struct Node
{
    int h;
    int w;
    Node(){}
    Node(int h,int w)
    {
        this->h=h;
        this->w=w;
    }
}s[100005];

class Solution {
public:
   
    int pos;
    int largestRectangleArea(vector<int>& heights) {
        
        if(heights.size()==0)
            return 0;
        
        pos=0;
        int res=heights[0];
        
        s[0]=Node(heights[0],1);
        
        for(int i=1;i<heights.size();i++)
        {
            if(heights[i]>s[pos].h)
            {
                s[++pos]=Node(heights[i],1);
            }
            else
            {
                int num=0;
                while(pos!=-1&&heights[i]<=s[pos].h)
                {
                    num+=s[pos].w;
                    res=max(res,s[pos].h*num);
                    pos--;
                }
                
                s[++pos]=Node(heights[i],num+1);
            }
        }
        
        int num=0;
        while(pos!=-1)
        {
            num+=s[pos].w;
            res=max(res,s[pos].h*num);
            pos--;
        }
        
        return res;
        
    }
};