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| // @Title: 课程表 II (Course Schedule II)
// @Author: 15816537946@163.com
// @Date: 2019-09-09 18:07:36
// @Runtime: 28 ms
// @Memory: 6.6 MB
func findOrder(numCourses int, prerequisites [][]int) []int {
next := make([][]int, numCourses)
for _, pair := range prerequisites {
next[pair[1]] = append(next[pair[1]], pair[0])
}
pres := make([]int, len(next))
for _, k := range next {
for _, v := range k {
pres[v]++
}
}
var i, j int
n := numCourses
ret := make([]int, n)
for i = 0; i < n; i++ {
for j = 0; j < n; j++ {
if pres[j] == 0 {
break
}
}
// 出现环路
if j >= numCourses {
return nil
}
pres[j] = -1
for _, c := range next[j] {
pres[c]--
}
ret[i] = j
}
return ret
}
|