# 85. Maximal Rectangle

### Description

Given a 2D binary matrix filled with 0's and 1's, find the largest rectangle containing only 1's and return its area.

### Constraints

### Approach

### Links

* GeeksforGeeks
* [Leetcode](https://leetcode.com/problems/maximal-rectangle/)
* [ProgramCreek](https://www.programcreek.com/2014/05/leetcode-maximal-rectangle-java/)
* [YouTube](https://youtu.be/g8bSdXCG-lA)

### **Examples**

{% tabs %}
{% tab title="Example 1" %}
**Input:**

\[

\["1", "0", "1", "0", "0"],

\["1", "0", "**1**", "**1**", "**1**"],

\["1", "1", "**1**", "**1**", "**1**"],

\["1", "0", "0", "1", "0"]

]

**Output:** 6
{% endtab %}
{% endtabs %}

### **Solutions**

{% tabs %}
{% tab title="Solution 1" %}

```java
/**
 * Time complexity : O(row*column)
 * Space complexity : O(column)
 */

class Solution {
    public int maximalRectangle(char[][] matrix) {
        if(matrix == null || 
           matrix.length == 0 || 
           matrix[0].length == 0) return 0;
        
        int m = matrix.length, n = matrix[0].length;
        int[] heights = new int[n];
        
        int maxRect = 0;
        for(int i = 0; i < m; i++) {
            for(int j = 0; j < n; j++) {
                int value = matrix[i][j]-'0';
                heights[j] = (value == 0)? 0: (value + heights[j]);
            }
            maxRect = Math.max(maxRect, largestRectangleArea(heights));
        }
        return maxRect;
    }
    
    private int largestRectangleArea(int[] heights) {
        Stack<Integer> stack = new Stack<>();
        int i = 0, area = 0;
        
        while(i < heights.length) {
            if(stack.isEmpty() || heights[stack.peek()] <= heights[i]) {
                stack.add(i++);
            } else {
                area = Math.max(area, calculateArea(stack, heights, i));
            }
        }
        
        while(!stack.isEmpty()) {
            area = Math.max(area, calculateArea(stack, heights, i));
        }
        
        return area;
    }

    private int calculateArea(Stack<Integer> stack, int[] heights, int i) {
        int height = heights[stack.pop()];
        int weight = (stack.isEmpty())? i: (i-stack.peek()-1);
        return height * weight;
    }
}
```

{% endtab %}
{% endtabs %}

### **Follow up**

*


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://code-snippets.hbamithkumara.com/leetcode/problems/1-100/maximal-rectangle.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.