bellman ford

package main

import "fmt"

// bellman ford 算法计算单源点到其他点的距离，它无法处理含有负权回路的图
func main() {
	type edge struct {
		from, to, weight int
	}
	graphs := []edge{
		{from: 0, to: 1, weight: 6},
		{from: 1, to: 2, weight: -2},
		{from: 0, to: 2, weight: 3},
		{from: 2, to: 3, weight: 5},
		{from: 3, to: 1, weight: 7},
	}

	max := 0x3f3f3f3f
	distance := make([]int, len(graphs))

	m := len(graphs)     // 边数, 暂时手动设置
	n := len(graphs) - 1 // 顶点数， 暂时手动设置

	for i := 0; i < n; i++ {
		distance[i] = max
	}
	distance[0] = 0 // 自己到自己的距离是0

	for i := 0; i < n; i++ {
		for j := 0; j < m; j++ {
			if distance[graphs[j].from] < max {
				distance[graphs[j].to] = min(distance[graphs[j].to], distance[graphs[j].from]+graphs[j].weight)
			}
		}
	}

	flag := false
	for i := 0; i < n; i++ {
		if distance[graphs[i].to] > distance[graphs[i].from]+graphs[i].weight {
			flag = true
		}
	}
	if flag {
		fmt.Println("含有负权回路")
		return
	}

	fmt.Println(distance[:n]) //return [0 6 3 8]
}

func min(a int, b int) int {
	if a < b {
		return a
	}
	return b
}
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