Rotting Oranges

Asked byAmazonMicrosoftVMwareLinkedIn

Problem

Given a grid where each cell is empty (0), a fresh orange (1), or a rotten orange (2), every minute any fresh orange adjacent to a rotten one becomes rotten. Return the minimum number of minutes until no fresh orange remains, or -1 if that's impossible.

Examples

Example 1

Input:grid = [[2,1,1],[1,1,0],[0,1,1]]

Output:4

Constraints

1 <= m, n <= 10

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How to approach it: the Graphs pattern

A graph models relationships as nodes and edges, which can be directed or undirected, weighted or not. Most graph problems come down to choosing the right traversal — DFS, BFS, or union-find — for what you're trying to find.

Look for this pattern when

The problem involves connections between items (islands, courses with prerequisites, friend networks, grids).
You need the shortest path in an unweighted graph (BFS) or need to explore every reachable node (DFS).
You're asking "are these two things connected?" repeatedly (union-find).

Read the full Graphs guide →

Video walkthroughs

Original problem on LeetCode ↗