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LeetCode solutions

1036. Rotting Oranges

My accepted Python solution to LeetCode problem 1036, Rotting Oranges, running in 3ms.

  • Difficulty: Medium
  • Python
  • Runtime 3ms
  • Memory 17.5MB

Read the problem on LeetCode View on GitHub

The problem statement is LeetCode’s and stays on their site. What follows is my accepted solution.

Python

Accepted on LeetCode — runtime 3ms, memory 17.5MB, accepted 2026-01-02.

python
class Solution:
    def orangesRotting(self, grid: List[List[int]]) -> int:
        from collections import deque
        
        rows, cols = len(grid), len(grid[0])
        queue = deque()
        fresh = 0
        
        # Find all rotten oranges and count fresh ones
        for r in range(rows):
            for c in range(cols):
                if grid[r][c] == 2:
                    queue.append((r, c, 0))
                elif grid[r][c] == 1:
                    fresh += 1
        
        # If no fresh oranges, return 0
        if fresh == 0:
            return 0
        
        # BFS
        directions = [(0, 1), (0, -1), (1, 0), (-1, 0)]
        time = 0
        
        while queue:
            r, c, t = queue.popleft()
            time = max(time, t)
            
            for dr, dc in directions:
                nr, nc = r + dr, c + dc
                if 0 <= nr < rows and 0 <= nc < cols and grid[nr][nc] == 1:
                    grid[nr][nc] = 2
                    fresh -= 1
                    queue.append((nr, nc, t + 1))
        
        return time if fresh == 0 else -1

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