- This is the "Shortest Path Faster" algorithm, an improvement on the Bellman-Ford algorithm.
- It operates on a directed graph with n nodes: 0, 1, ..., n-1. Each graph edge has a distance.
- Negative edge distances are permitted, in contrast to Dijkstra's shortest path algorithm.
- len(arcs) is n and outgoing edges from node i are described by pairs of integers in arcs[i].
- If node i1 has an edge to node i2 with distance d2 then arcs[i1] contains the pair (i2, d2).
- All nodes reachable from root get an entry in the output map. Unreachable nodes are omitted.

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