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44 lines
863 B
Go
44 lines
863 B
Go
// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
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// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
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// See page 99.
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// Graph shows how to use a map of maps to represent a directed graph.
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package main
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import "fmt"
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//!+
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var graph = make(map[string]map[string]bool)
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func addEdge(from, to string) {
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edges := graph[from]
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if edges == nil {
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edges = make(map[string]bool)
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graph[from] = edges
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}
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edges[to] = true
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}
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func hasEdge(from, to string) bool {
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return graph[from][to]
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}
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//!-
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func main() {
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addEdge("a", "b")
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addEdge("c", "d")
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addEdge("a", "d")
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addEdge("d", "a")
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fmt.Println(hasEdge("a", "b"))
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fmt.Println(hasEdge("c", "d"))
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fmt.Println(hasEdge("a", "d"))
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fmt.Println(hasEdge("d", "a"))
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fmt.Println(hasEdge("x", "b"))
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fmt.Println(hasEdge("c", "d"))
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fmt.Println(hasEdge("x", "d"))
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fmt.Println(hasEdge("d", "x"))
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}
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