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noc.go
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noc.go
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package noc
import (
"github.com/catorpilor/leetcode/utils"
)
func CountComponents(n int, edges [][]int) int {
if n <= 1 {
return n
}
// weighted union-find with path compression
ids := make([]int, n)
wz := make([]int, n)
for i := range ids {
ids[i] = i
wz[i] = 1
}
root := func(p int) int {
for p != ids[p] {
ids[p] = ids[ids[p]]
p = ids[p]
}
return p
}
union := func(i, j int) {
if wz[i] < wz[j] {
ids[i] = j
wz[j] += wz[i]
} else {
ids[j] = i
wz[i] += wz[j]
}
}
ret := n
for _, v := range edges {
r1, r2 := root(v[0]), root(v[1])
if r1 != r2 {
union(r1, r2)
ret--
}
}
return ret
}
func CountComponents2(n int, edges [][]int) int {
if n <= 1 {
return n
}
g := make(map[int][]int)
for _, v := range edges {
g[v[0]] = append(g[v[0]], v[1])
g[v[1]] = append(g[v[1]], v[0])
}
visited := make([]bool, n)
var ret int
for i := 0; i < n; i++ {
if !visited[i] {
dfs(g, &visited, i)
ret++
}
}
return ret
}
func dfs(g map[int][]int, visited *[]bool, node int) {
(*visited)[node] = true
for _, n := range g[node] {
if !(*visited)[n] {
dfs(g, visited, n)
}
}
}
func CountComponents3(n int, edges [][]int) int {
if n <= 1 {
return n
}
g := make(map[int][]int)
for _, v := range edges {
g[v[0]] = append(g[v[0]], v[1])
g[v[1]] = append(g[v[1]], v[0])
}
visited := make([]bool, n)
var ret int
q := utils.NewQueue()
for i := 0; i < n; i++ {
if !visited[i] {
q.Enroll(i)
for !q.IsEmpty() {
k := q.Pull().(int)
visited[k] = true
for _, v := range g[k] {
if !visited[v] {
q.Enroll(v)
}
}
}
ret++
}
}
return ret
}