結果

問題 No.1254 補強への架け橋
ユーザー 草苺奶昔
提出日時 2023-03-24 15:20:36
言語 Go
(1.23.4)
結果
AC  
実行時間 269 ms / 2,000 ms
コード長 3,951 bytes
コンパイル時間 11,649 ms
コンパイル使用メモリ 223,272 KB
実行使用メモリ 43,904 KB
最終ジャッジ日時 2024-09-18 16:28:03
合計ジャッジ時間 27,078 ms
ジャッジサーバーID
（参考情報） 		judge2 / judge1
このコードへのチャレンジ
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ファイルパターン 結果
sample AC * 3
other AC * 123
権限があれば一括ダウンロードができます

ソースコード

diff #
プレゼンテーションモードにする

package main
import (
    "bufio"
    "fmt"
    "os"
    "sort"
)
func main() {
    in := bufio.NewReader(os.Stdin)
    out := bufio.NewWriter(os.Stdout)
    defer out.Flush()
    var n int
    fmt.Fscan(in, &n)
    g := make([][]Edge, n)
    for i := 0; i < n; i++ {
        var a, b int
        fmt.Fscan(in, &a, &b)
        a--
        b--
        g[a] = append(g[a], Edge{a, b, 1, i})
        g[b] = append(g[b], Edge{b, a, 1, i})
    }
    ng := NewNamoriGraph(g)
    ng.Build()
    res := []int{}
    for _, e := range ng.CycleEdges {
        res = append(res, e.id+1)
    }
    sort.Ints(res)
    fmt.Fprintln(out, len(res))
    for _, v := range res {
        fmt.Fprint(out, v, " ")
    }
}
type NamoriGraph struct {
    // !以环上各个顶点i为根的无向树
    Trees []Graph
    // !基环树中在环上的边,边i连接着树的 root i和i+1 (i>=0)
    CycleEdges []Edge
    g          Graph
    iv         [][]int
    markId, id []int
}
type Edge = struct{ from, to, cost, id int }
type Graph = [][]Edge
func NewNamoriGraph(g Graph) *NamoriGraph {
    return &NamoriGraph{g: g}
}
func (ng *NamoriGraph) Build() {
    n := len(ng.g)
    deg := make([]int, n)
    used := make([]bool, n)
    que := []int{}
    for i := 0; i < n; i++ {
        deg[i] = len(ng.g[i])
        if deg[i] == 1 {
            que = append(que, i)
            used[i] = true
        }
    }
    for len(que) > 0 {
        idx := que[0]
        que = que[1:]
        for _, e := range ng.g[idx] {
            if used[e.to] {
                continue
            }
            deg[e.to]--
            if deg[e.to] == 1 {
                que = append(que, e.to)
                used[e.to] = true
            }
        }
    }
    mx := 0
    for _, edges := range ng.g {
        for _, e := range edges {
            mx = max(mx, e.id)
        }
    }
    edgeUsed := make([]bool, mx+1)
    loop := []int{}
    for i := 0; i < n; i++ {
        if used[i] {
            continue
        }
        for update := true; update; {
            update = false
            loop = append(loop, i)
            for _, e := range ng.g[i] {
                if used[e.to] || edgeUsed[e.id] {
                    continue
                }
                edgeUsed[e.id] = true
                ng.CycleEdges = append(ng.CycleEdges, Edge{i, e.to, e.cost, e.id})
                i = e.to
                update = true
                break
            }
        }
        break
    }
    loop = loop[:len(loop)-1]
    ng.markId = make([]int, n)
    ng.id = make([]int, n)
    for i := 0; i < len(loop); i++ {
        pre := loop[(i+len(loop)-1)%len(loop)]
        nxt := loop[(i+1)%len(loop)]
        sz := 0
        ng.markId[loop[i]] = i
        ng.iv = append(ng.iv, []int{})
        ng.id[loop[i]] = sz
        sz++
        ng.iv[len(ng.iv)-1] = append(ng.iv[len(ng.iv)-1], loop[i])
        for _, e := range ng.g[loop[i]] {
            if e.to != pre && e.to != nxt {
                ng.markDfs(e.to, loop[i], i, &sz)
            }
        }
        tree := make(Graph, sz)
        for _, e := range ng.g[loop[i]] {
            if e.to != pre && e.to != nxt {
                tree[ng.id[loop[i]]] = append(tree[ng.id[loop[i]]], Edge{ng.id[loop[i]], ng.id[e.to], e.cost, e.id})
                tree[ng.id[e.to]] = append(tree[ng.id[e.to]], Edge{ng.id[e.to], ng.id[loop[i]], e.cost, e.id})
                ng.buildDfs(e.to, loop[i], tree)
            }
        }
        ng.Trees = append(ng.Trees, tree)
    }
}
// 给定原图的顶点rawV,返回rawV所在的树的根节点和rawV在树中的编号.
func (ng *NamoriGraph) GetId(rawV int) (rootId, idInTree int) {
    return ng.markId[rawV], ng.id[rawV]
}
// 给定树的顶点编号root和某个点在树中的顶点编号idInTree,返回这个点在原图中的顶点编号.
//  GetInvId(root,0) 表示在环上的顶点root在原图中对应的顶点.
func (ng *NamoriGraph) GetInvId(rootId, idInTree int) (rawV int) {
    return ng.iv[rootId][idInTree]
}
func (ng *NamoriGraph) markDfs(idx, par, k int, l *int) {
    ng.markId[idx] = k
    ng.id[idx] = *l
    *l++
    ng.iv[len(ng.iv)-1] = append(ng.iv[len(ng.iv)-1], idx)
    for _, e := range ng.g[idx] {
        if e.to != par {
            ng.markDfs(e.to, idx, k, l)
        }
    }
}
func (ng *NamoriGraph) buildDfs(idx, par int, tree Graph) {
    for _, e := range ng.g[idx] {
        if e.to != par {
            tree[ng.id[idx]] = append(tree[ng.id[idx]], Edge{ng.id[idx], ng.id[e.to], e.cost, e.id})
            tree[ng.id[e.to]] = append(tree[ng.id[e.to]], Edge{ng.id[e.to], ng.id[idx], e.cost, e.id})
            ng.buildDfs(e.to, idx, tree)
        }
    }
}
func max(a, b int) int {
    if a > b {
        return a
    }
    return b
}
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