# [Solved] Given a rows x cols binary matrix filled with 0’s and 1’s, find the largest rectangle containing only 1’s and return its area.

## Question

Given a `rows x cols` binary `matrix` filled with `0`‘s and `1`‘s, find the largest rectangle containing only `1`‘s and return its area.

Example 1:

```Input: matrix = [["1","0","1","0","0"],["1","0","1","1","1"],["1","1","1","1","1"],["1","0","0","1","0"]]
Output: 6
Explanation: The maximal rectangle is shown in the above picture.
```

Example 2:

```Input: matrix = [["0"]]
Output: 0
```

Example 3:

```Input: matrix = [["1"]]
Output: 1
```

Constraints:

• `rows == matrix.length`
• `cols == matrix[i].length`
• `1 <= row, cols <= 200`
• `matrix[i][j]` is `'0'` or `'1'`.

## Python Solution

```class Solution:
def maximalRectangle(self, rect: List[List[str]]) -> int:
def largestRectangleArea(A):
stack = []
maxi = 0
i = 0
while i<len(A):
if len(stack)==0 or A[stack[-1]]<=A[i]:
stack.append(i)
i+=1
else:
top = stack.pop()
if len(stack)==0:
ar = A[top]*(i)
else:
ar = A[top]*(i-stack[-1]-1)
maxi = max(maxi,ar)

while len(stack)!=0:
top = stack.pop()
if len(stack)==0:
ar = A[top]*(i)
else:
ar = A[top]*(i-stack[-1]-1)
maxi = max(maxi,ar)

return(maxi)

if rect==[]:return 0
rows = len(rect)
cols = len(rect)
for i in range(rows):
for j in range(cols):
rect[i][j] = int(rect[i][j])

m = largestRectangleArea(rect)

for i in range(1,rows):
for j in range(cols):
if rect[i][j]==1:
rect[i][j] = rect[i-1][j]+1
m = max(m,largestRectangleArea(rect[i]))

return (m)``` ##### Abhishek Sharma

Started my Data Science journey in my 2nd year of college and since then continuously into it because of the magical powers of ML and continuously doing projects in almost every domain of AI like ML, DL, CV, NLP.

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