Exercise 3: Check Neighbors

Your Task

Write a function count_neighbors(grid, row, col, value) that returns how many of the 4 adjacent cells (up, down, left, right) equal value.

Be careful at the edges — don't go out of bounds!

Examples

grid = [
    [1, 2, 1],
    [2, 5, 2],
    [1, 2, 1]
]

print(count_neighbors(grid, 1, 1, 2))  # 4 — all 4 neighbors of center are 2
print(count_neighbors(grid, 0, 0, 2))  # 1 — top-left corner, only right neighbor is 2
print(count_neighbors(grid, 1, 1, 1))  # 0 — center has no neighbors equal to 1

Hints

💡 Hint

Use the four-directions pattern from the intro:

directions = [(-1, 0), (1, 0), (0, -1), (0, 1)]

For each direction, compute the new position and check:

Is it in bounds?
Does it equal value?

✅ Solution

def count_neighbors(grid, row, col, value):
    rows, cols = len(grid), len(grid[0])
    directions = [(-1, 0), (1, 0), (0, -1), (0, 1)]
    count = 0
    for dr, dc in directions:
        r, c = row + dr, col + dc
        if 0 <= r < rows and 0 <= c < cols:
            if grid[r][c] == value:
                count += 1
    return count

Check Neighbors

Exercise 3: Check Neighbors

Your Task

Examples

Hints

Try it yourself

Code: Check Neighbors