Set Matrix Zeroes - Optimal Approach

Algorithm Steps

Given a 2D matrix mat.
Use the first row and first column as markers to indicate if a row or column should be set to zero.
Check if the first row and first column themselves contain any zero using two separate flags.
Traverse the rest of the matrix:
→ If any element is 0, mark its row and column in the first row and column.
Traverse the matrix again (excluding first row and column):
→ If mat[i][0] == 0 or mat[0][j] == 0, set mat[i][j] = 0.
Finally, update the first row and first column based on the flags.

Set Matrix Zeroes Using Constant Space Code

Python

JavaScript

Java

C++

def set_zeroes(matrix):
    rows, cols = len(matrix), len(matrix[0])
    first_row_zero = any(matrix[0][j] == 0 for j in range(cols))
    first_col_zero = any(matrix[i][0] == 0 for i in range(rows))

    for i in range(1, rows):
        for j in range(1, cols):
            if matrix[i][j] == 0:
                matrix[i][0] = 0
                matrix[0][j] = 0

    for i in range(1, rows):
        for j in range(1, cols):
            if matrix[i][0] == 0 or matrix[0][j] == 0:
                matrix[i][j] = 0

    if first_row_zero:
        for j in range(cols):
            matrix[0][j] = 0

    if first_col_zero:
        for i in range(rows):
            matrix[i][0] = 0

    return matrix

# Sample Input
mat = [[1,1,1],[1,0,1],[1,1,1]]
print("Updated Matrix:", set_zeroes(mat))