LeetCode 743 Network Delay Time - Intuition

The signal travels to all nodes simultaneously. The time it takes for node $x$ to get the signal is the shortest path from $k$ to $x$. Run Dijkstra from source $k$. Find dist[x] for all nodes.

The answer is max(dist[x]) over all $x$. If any dist[x] = Infinity, return $-1$. This problem is direct Dijkstra application. No tricks, implement it correctly. Good for practice. Watch out for $1$-indexed vs $0$-indexed node numbering in the input.