golang力扣leetcode 207.课程表

func canFinish(numCourses int, prerequisites [][]int) bool {
  indeg := make([]int, numCourses)
  mp := make(map[int][]int)
  queue := make([]int, 0)
  for _, v := range prerequisites {
    indeg[v[1]]++
    mp[v[0]] = append(mp[v[0]], v[1])
  }
  for i, v := range indeg {
    if v == 0 {
      queue = append(queue, i)
    }
  }
  for len(queue) != 0 {
    top := queue[0]
    queue = queue[1:]
    v := mp[top]
    delete(mp, top)
    for _, vv := range v {
      indeg[vv]--
      if indeg[vv] == 0 {
        queue = append(queue, vv)
      }
    }
  }
  cnt := 0
  for _, v := range indeg {
    cnt += v
  }
  return cnt == 0
}