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How to Build a Coordinate Grid with Nested Loops in Python

Generate a 2D list of (row, col) coordinate pairs using nested loops and return the grid structure.

def build_coordinate_grid(rows, cols):
    """Build a 2D grid of (row, col) coordinates using nested loops."""
    grid = []
    for r in range(rows):
        row = []
        for c in range(cols):
            row.append((r, c))
        grid.append(row)
    return grid


if __name__ == "__main__":
    grid = build_coo…

15 0 Open

Algorithms & data structures medium

Set Matrix Zeroes in Python: Markers List Grid Demo

Given a matrix, this code finds all rows and columns that contain a zero and sets every element in those rows and columns to zero, using boolean marker arrays.

matrix arrays algorithm

Python

def set_zeroes(matrix):
    rows, cols = len(matrix), len(matrix[0])
    row_markers = [False] * rows
    col_markers = [False] * cols

    # First pass: record which rows and columns contain zeros
    for i in range(rows):
        for j in range(cols):
            if matrix[i][j] == 0:
                row_markers[i] …

14 0 Open

Algorithms & data structures medium

Validate Sudoku Board Rows Columns and Boxes in Python

Validate a 9x9 Sudoku board by checking that each row, column, and 3x3 box contains the numbers 1 through 9 exactly once.

sudoku validation matrix

Python

def validate_sudoku(board):
    def is_valid_group(group):
        return sorted(group) == list(range(1, 10))

    def get_columns():
        return [[board[r][c] for r in range(9)] for c in range(9)]

    def get_boxes():
        boxes = []
        for box_row in range(0, 9, 3):
            for box_col in range(0, 9,…

11 0 Open

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