Go语言圣经练习5.11_golang 线性代数-优快云博客

本文链接：https://blog.youkuaiyun.com/mmmm433/article/details/103496429

本文介绍使用Go语言实现的算法，用于检测有向图中的环，通过深度优先搜索和递归标记节点来判断图中是否存在环路，并提供了一个具体的代码示例，展示了如何在课程先决条件图中应用此算法。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

Go语言圣经练习5.11

练习5.11

现在线性代数的老师把微积分设为了前置课程。完善topSort，使其能检测有向图
中的环。

关于在有向图中检测环，参考下面文章：
https://blog.youkuaiyun.com/anlian523/article/details/81806384

Go实现代码如下：


```go
 func main() {
	var prereqs = map[string][]string{
		"algorithms": {"data structures"},
		"calculus":   {"linear algebra"},
		"compilers": {
			"data structures",
			"formal languages",
			"computer organization",
		},
		"data structures":       {"discrete math"},
		"databases":             {"data structures"},
		"discrete math":         {"intro to programming"},
		"formal languages":      {"discrete math"},
		"networks":              {"operating systems"},
		"operating systems":     {"data structures", "computer organization"},
		"programming languages": {"data structures", "computer organization"},
		"linear algebra":        {"calculus"},
	}
	var findCycle func(m map[string][]string, v string, marked map[string]bool, deep int, trace map[int]string) bool
	findCycle = func(m map[string][]string, v string, marked map[string]bool, deep int, trace map[int]string) bool {
		marked[v] = true //标记该课程已经访问
		deep++ //deep是递归的深度，也记录整个课程的顺序
		trace[deep] = v //trace记录整个课程顺序与课程名
		for _, it := range m[v] { //对该课程（v）的每一个邻居（前置课程）进行遍历
			if !marked[it] {
				if findCycle(m, it, marked, deep, trace) {//深度优先递归遍历
					return true
				}
			} else {
				if marked[it] {//已经访问的课程说明存在环
					return true
				}
			}
		}
		//如果没有环，那么以上循环会以递归树执行，而且不会return，所以会返回下面的终点
		marked[v] = false 
		return false
	}
	var allkeys []string
	for k := range prereqs {
		allkeys = append(allkeys, k)
	}
	for k := range prereqs {
		marked := make(map[string]bool) 
		trace := make(map[int]string)
		i := 0
		fmt.Printf("Course: %s\n", k)
		fmt.Printf("Contains Cycle: %t\n", findCycle(prereqs, k, marked, i, trace))
		var sortedkeys []int
		for k := range trace {
			sortedkeys = append(sortedkeys, k)
		}
		sort.Ints(sortedkeys)
		for _, k := range sortedkeys {
			if k == len(sortedkeys) {
				fmt.Printf("%d/%d %s", k, len(sortedkeys), trace[k])

			} else {
				fmt.Printf("%d/%d %s -> ", k, len(sortedkeys), trace[k])
			}
		}
		fmt.Printf("\n************************************\n")
	}
}


结果如下：
https://img-blog.csdnimg.cn/20191211172916970.jpg
![在这里插入图片描述](https://img-blog.csdnimg.cn/20191211172916970.jpg?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21tbW00MzM=,size_16,color_FFFFFF,t_70)