golang[4]-数据结构-拓扑排序-深度优先搜索

拓扑排序

排序前序课程、深度优先搜索

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// The toposort program prints the nodes of a DAG in topological order.
package main

import (
"fmt"
"sort"
)

//!+table
// prereqs maps computer science courses to their prerequisites.
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"},
}

//!-table

//!+main
func main() {
for i, course := range topoSort(prereqs) {
fmt.Printf("%d:\t%s\n", i+1, course)
}
}

func topoSort(m map[string][]string) []string {
var order []string
seen := make(map[string]bool)
var visitAll func(items []string)

visitAll = func(items []string) {
for _, item := range items {
if !seen[item] {
seen[item] = true
visitAll(m[item])
order = append(order, item)
}
}
}

var keys []string
for key := range m {
keys = append(keys, key)
}

sort.Strings(keys)
visitAll(keys)
return order
}