84 lines
2.3 KiB
Go
84 lines
2.3 KiB
Go
package main
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import (
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"Study/src/study/day7Function/HtmlTools"
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"fmt"
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"log"
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)
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// 接下来，我们讨论一个有点学术性的例子，考虑这样一个问题：
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// 给定一些计算机课程，每个课程都有前置课程，只有完成了前置课程才可以开始当前课程的学习；
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// 我们的目标是选择出一组课程，这组课程必须确保按顺序学习时，能全部被完成。每个课程的前置课程如下：
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// prereqs记录了每个课程的前置课程
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var prereqs = map[string][]string{
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"algorithms": {"data structures"},
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"linear algebra": {"calculus"},
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"calculus": {"linear algebra"},
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"compilers": {
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"data structures",
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"formal languages",
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"computer organization",
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},
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"data structures": {"discrete math"},
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"databases": {"data structures"},
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"discrete math": {"intro to programming"},
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"formal languages": {"discrete math"},
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"networks": {"operating systems"},
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"operating systems": {"data structures", "computer organization"},
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"programming languages": {"data structures", "computer organization"},
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}
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func main() {
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// for i, course := range topoSort(prereqs) {
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// fmt.Printf("%d:\t%s\n", i, course)
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// }
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//fmt.Println(hasCycle(prereqs))
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//topoSort(prereqs)
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//fmt.Printf("%v", len(prereqs["qqq"]))
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//BreadthFirst(crawl, []string{"all"})
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}
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// BreadthFirst
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// calls f() for each item in the worklist.
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// Any items returned by f() are added to the worklist.
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// f() is called at most once for each item.
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//
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// -
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//
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// BreadthFirst 队列中的每节点都调用f()。
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// f()返回的所有节点都被添加到队列中。
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// 对每个节点最多调用一次f()。
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//
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// f func(item string) []string
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// returns []string
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func BreadthFirst(f func(item string) []string, worklist []string) {
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// seen
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seen := make(map[string]bool)
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for len(worklist) > 0 {
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// 复制当前队列
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items := worklist
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// 清空队列
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worklist = nil
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// 遍历复制的当前队列
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for _, item := range items {
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// 判断seen, 防止重复添加到队列
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if !seen[item] {
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seen[item] = true
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// 添加到队列
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worklist = append(worklist, f(item)...)
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}
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}
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}
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}
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// crawl 此函数返回一个[]string, 内容为url
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func crawl(url string) []string {
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fmt.Println(url)
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list, err := HtmlTools.Extract()
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if err != nil {
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log.Print(err)
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}
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return list
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}
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