Assume there is an algorithm that solves the single-source shortest path problem in O(n+m) time for directed graphs with

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Assume there is an algorithm that solves the single-sourceshortest path problem in O(n+m) time for directed graphs with nvertices, m edges, and non-negative integer edge weights. Let'scall this algorithm SHORT.
Using SHORT, design a O(n+m) algorithm for an adjacency listrepresentation of an unweighted directed graph G. Given twodesignated vertices s, t ∈ V and a subset B ⊆ V of the vertices arelabeled as “purple” vertices. Find a path from s to t that visitsas few purple vertices as possible