Shortest Path with Alternating Colors(LeetCode 1129):

Problem

You are given an integer n, the number of nodes in a directed graph where the nodes are labeled from 0 to n - 1. Each edge is red or blue in this graph, and there could be self-edges and parallel edges.

You are given two arrays redEdges and blueEdges where:

  • redEdges[i] = [ai, bi] indicates that there is a directed red edge from node ai to node bi in the graph, and
  • blueEdges[j] = [uj, vj] indicates that there is a directed blue edge from node uj to node vj in the graph.

Return an array answer of length n, where each answer[x] is the length of the shortest path from node 0 to node x such that the edge colors alternate along the path, or -1 if such a path does not exist.

 

Example 1:

Input: n = 3, redEdges = [[0,1],[1,2]], blueEdges = []
Output: [0,1,-1]

Example 2:

Input: n = 3, redEdges = [[0,1]], blueEdges = [[2,1]]
Output: [0,1,-1]

 

Constraints:

  • 1 <= n <= 100
  • 0 <= redEdges.length, blueEdges.length <= 400
  • redEdges[i].length == blueEdges[j].length == 2
  • 0 <= ai, bi, uj, vj < n