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| // @Title: 保证图可完全遍历 (Remove Max Number of Edges to Keep Graph Fully Traversable)
// @Author: 15816537946@163.com
// @Date: 2021-01-27 23:52:48
// @Runtime: 380 ms
// @Memory: 19 MB
type unionFind struct {
parent, size []int
setCount int // 当前连通分量数目
}
func newUnionFind(n int) *unionFind {
parent := make([]int, n)
size := make([]int, n)
for i := range parent {
parent[i] = i
size[i] = 1
}
return &unionFind{parent, size, n}
}
func (uf *unionFind) find(x int) int {
if uf.parent[x] != x {
uf.parent[x] = uf.find(uf.parent[x])
}
return uf.parent[x]
}
func (uf *unionFind) union(x, y int) bool {
fx, fy := uf.find(x), uf.find(y)
if fx == fy {
return false
}
if uf.size[fx] < uf.size[fy] {
fx, fy = fy, fx
}
uf.size[fx] += uf.size[fy]
uf.parent[fy] = fx
uf.setCount--
return true
}
func (uf *unionFind) inSameSet(x, y int) bool {
return uf.find(x) == uf.find(y)
}
func maxNumEdgesToRemove(n int, edges [][]int) int {
ans := len(edges)
alice, bob := newUnionFind(n), newUnionFind(n)
for _, e := range edges {
x, y := e[1]-1, e[2]-1
if e[0] == 3 && (!alice.inSameSet(x, y) || !bob.inSameSet(x, y)) {
// 保留这条公共边
alice.union(x, y)
bob.union(x, y)
ans--
}
}
uf := [2]*unionFind{alice, bob}
for _, e := range edges {
if tp := e[0]; tp < 3 && uf[tp-1].union(e[1]-1, e[2]-1) {
// 保留这条独占边
ans--
}
}
if alice.setCount > 1 || bob.setCount > 1 {
return -1
}
return ans
}
|