# Largest Rectangle in Histogram LeetCode Solution

Here, We see Largest Rectangle in Histogram problem Solution. This Leetcode problem is done in many programming languages like C++, Java, JavaScript, Python, etc., with different approaches.

## Problem Statement ->

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: (fig-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: (fig-2)
Input: heights = [2,4]
Output: 4```

## Largest Rectangle in Histogram Leetcode Solution C++ ->

``````class Solution {
public:
int largestRectangleArea(vector<int>& heights) {
stack<int> st;
int ans=0;
heights.push_back(0);
for(int i=0;i<heights.size();i++){
while(!st.empty() && heights[st.top()]>heights[i]){
int top=heights[st.top()];
st.pop();
int ran=st.empty()?-1:st.top();
ans=max(ans,top*(i-ran-1));
}
st.push(i);
}
return ans;
}
};
```Code language: C++ (cpp)```

## Largest Rectangle in Histogram Leetcode Solution Java ->

``````class Solution {
public int largestRectangleArea(int[] heights) {
if (heights == null || heights.length == 0) {
return 0;
}
int[] lessFromLeft = new int[heights.length]; // idx of the first bar the left that is lower than current
int[] lessFromRight = new int[heights.length]; // idx of the first bar the right that is lower than current
lessFromRight[heights.length - 1] = heights.length;
lessFromLeft = -1;

for (int i = 1; i < heights.length; i++) {
int p = i - 1;
while (p >= 0 && heights[p] >= heights[i]) {
p = lessFromLeft[p];
}
lessFromLeft[i] = p;
}
for (int i = heights.length - 2; i >= 0; i--) {
int p = i + 1;

while (p < heights.length && heights[p] >= heights[i]) {
p = lessFromRight[p];
}
lessFromRight[i] = p;
}
int maxArea = 0;
for (int i = 0; i < heights.length; i++) {
maxArea = Math.max(maxArea, heights[i] * (lessFromRight[i] - lessFromLeft[i] - 1));
}
return maxArea;
}
}
```Code language: Java (java)```

## Largest Rectangle in Histogram Leetcode Solution JavaScript ->

``````var largestRectangleArea = function(heights) {
heights.push(0)
const stack = [];
let maxArea = 0, curr, currH, top, topH, area;

for(let i = 0; i < heights.length; i++) {
top = stack[stack.length-1];
topH = heights[top];
while(stack.length > 1 && topH > heights[i]) {
curr = stack.pop();
currH = heights[curr];
top = stack[stack.length-1];
topH = heights[top];
area = currH * (i - 1 - top);
maxArea = Math.max(area, maxArea);
}
if(stack.length && topH > heights[i]) {
curr = stack.pop();
currH = heights[curr];
area = currH * i;
maxArea = Math.max(area, maxArea);
}
stack.push(i);
}
return maxArea;
};
```Code language: JavaScript (javascript)```

## Largest Rectangle in Histogram Leetcode Solution Python ->

``````class Solution(object):
def largestRectangleArea(self, heights):
heights.append(0)
stack = [-1]
ans = 0
for i in xrange(len(heights)):
while heights[i] < heights[stack[-1]]:
h = heights[stack.pop()]
w = i - stack[-1] - 1
ans = max(ans, h * w)
stack.append(i)
heights.pop()
return ans
```Code language: Python (python)```

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