# Maximum size rectangle binary sub-matrix with all 1s in C++

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In this tutorial, we will be discussing a program to find maximum size rectangle binary sub-matrix with all 1s.

For this we will be provided with 2D matrix containing zeroes and ones. Our task is to find the largest 2D matrix subset containing only ones.

## Example

Live Demo

#include <bits/stdc++.h>
using namespace std;
#define R 4
#define C 4
//finding the maximum area
int maxHist(int row[]) {
stack<int> result;
int top_val;
int max_area = 0;
int area = 0;
int i = 0;
while (i < C) {
if (result.empty() || row[result.top()] <= row[i])
result.push(i++);
else {
top_val = row[result.top()];
result.pop();
area = top_val * i;
if (!result.empty())
area = top_val * (i - result.top() - 1);
max_area = max(area, max_area);
}
}
while (!result.empty()) {
top_val = row[result.top()];
result.pop();
area = top_val * i;
if (!result.empty())
area = top_val * (i - result.top() - 1);
max_area = max(area, max_area);
}
return max_area;
}
//returning area of largest required subset
int maxRectangle(int A[][C]) {
int result = maxHist(A);
for (int i = 1; i < R; i++) {
for (int j = 0; j < C; j++)
if (A[i][j])
A[i][j] += A[i - 1][j];
result = max(result, maxHist(A[i]));
}
return result;
}
int main() {
int A[][C] = {
{ 0, 1, 1, 0 },{ 1, 1, 1, 1 },{ 1, 1, 1, 1 },{ 1, 1, 0, 0 },
};
cout << "Area of maximum rectangle is " <<
maxRectangle(A);
return 0;
}

## Output

Area of maximum rectangle is 8