84. Largest Rectangle in Histogram | LeetCode Solution

84. Largest Rectangle in Histogram | LeetCode Solution 

Given an array of integers heights representing the histogram's bar height where the width of each bar is 1, return the area of the largest rectangle in the histogram.

 

Example 1:

Input: heights = [2,1,5,6,2,3]
Output: 10
Explanation: The above is a histogram where width of each bar is 1.
The largest rectangle is shown in the red area, which has an area = 10 units.

Example 2:

Input: heights = [2,4]
Output: 4

 

Constraints:

• 1 <= heights.length <= 105
• 0 <= heights[i] <= 104

class Solution

{

public:

    int largestRectangleArea(vector<int> &v)

    {

        stack<int> st;

        int n = v.size();

        int ans = 0;

        for (int i = 0; i <= n; i++)

        {

            while (!st.empty() && (i == n || v[st.top()] >= v[i]))

            {

                int height = v[st.top()];

                int width;

                st.pop();

                if (st.empty())

                    width = i;

                else

                    width = i - st.top() - 1;

                ans = max(ans, height * width);

            }

            st.push(i);

        }

        return ans;

    }

};