-
Notifications
You must be signed in to change notification settings - Fork 0
/
go_dijkstras.go
79 lines (65 loc) · 1.96 KB
/
go_dijkstras.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
package main
import (
"fmt"
"math"
)
/*
狄克斯特拉算法
(1)找出“最便宜”的节点,即可在最短时间内到达的节点。
(2)更新该节点的邻居的开销,其含义将稍后介绍。
(3)重复这个过程,直到对图中的每个节点都这样做了。
(4)计算最终路径。
*/
func dijkstras() {
graph := make(map[string]map[string]int)
graph["start"] = map[string]int{}
graph["start"]["a"] = 6
graph["start"]["b"] = 2
graph["a"] = map[string]int{}
graph["a"]["finish"] = 1
graph["b"] = map[string]int{}
graph["b"]["a"] = 3
graph["b"]["finish"] = 5
graph["finish"] = map[string]int{}
costs, parents := findShortestPath(graph, "start", "finish")
fmt.Println(costs, parents)
}
// Finds shortest path using dijkstra algorithm
func findShortestPath(graph map[string]map[string]int, startNode string, finishNode string) (map[string]int, map[string]string) {
costs := make(map[string]int)
costs[finishNode] = math.MaxInt32
parents := make(map[string]string)
parents[finishNode] = ""
processed := make(map[string]bool)
// Initialization of costs and parents
for node, cost := range graph[startNode] {
costs[node] = cost
parents[node] = startNode
}
lowestCostNode := findLowestCostNode(costs, processed)
for ; lowestCostNode != "" ; {
// Calculation costs for neighbours
for node, cost := range graph[lowestCostNode] {
newCost := costs[lowestCostNode] + cost
if newCost < costs[node] {
// Set new cost for this node
costs[node] = newCost
parents[node] = lowestCostNode
}
}
processed[lowestCostNode] = true
lowestCostNode = findLowestCostNode(costs, processed)
}
return costs, parents
}
func findLowestCostNode(costs map[string]int, processed map[string]bool) string {
lowestCost := math.MaxInt32
lowestCostNode := ""
for node, cost := range costs {
if _, inProcessed := processed[node]; cost < lowestCost && !inProcessed {
lowestCost = cost
lowestCostNode = node
}
}
return lowestCostNode
}