Network Delay Time
Detailed guide and Python implementation for the 'Network Delay Time' problem.
Problem Statement
You are given a network of n nodes, labeled from 1 to n. You are also given times, a list of travel times as directed edges times[i] = [ui, vi, wi], where ui is the source node, vi is the target node, and wi is the time it takes for a signal to travel from source to target.
We will send a signal from a given node k. Return the minimum time it takes for all the n nodes to receive the signal. If it is impossible for all the n nodes to receive the signal, return -1.
Write a function networkDelayTime(times: List[List[int]], n: int, k: int) -> int.
- •1 <= k <= n <= 100
- •1 <= len(times) <= 6000
- •times[i].length == 3
- •1 <= ui, vi <= n
- •ui != vi
- •0 <= wi <= 100
- •All the pairs (ui, vi) are unique
Examples
times = [[2,1,1],[2,3,1],[3,4,1]], n = 4, k = 2
2
The signal starts at node 2. It reaches 1 and 3 in 1 unit of time, and 4 in 2 units of time.
times = [[1,2,1]], n = 2, k = 1
1
Signal reaches node 2 from node 1 in 1 unit of time.
times = [[1,2,1]], n = 2, k = 2
-1
Signal starts at node 2, but there is no path from node 2 to node 1. So node 1 never receives it.
Need a Hint?
Edge Cases to Watch
- Empty input structures
- Single element inputs
- Large numerical bounds
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