Submission #44753

#	Time	Username	Problem	Language	Result	Execution time	Memory
44753		RayaBurong25_1	Pipes (CEOI15_pipes)	C++17	0 / 100	60 ms	65536 KiB

pipes

#include <stdio.h>
#include <deque>
#include <queue>
std::deque<int> AdjList[100005];
int Vis[100005];
int p[100005];
int H[100005];
int Pa[17][100005];
int mark[100005];
std::queue<std::pair<int, int>> Q;
int UF(int u)
{
    return (p[u] == 0)?u:(p[u] = UF(p[u]));
}
void dfs(int u, int pa, int h)
{
    // printf("dfs u%d pa%d h%d\n", u, pa, h);
    Vis[u] = 1;
    H[u] = h;
    Pa[0][u] = pa;
    int i, v, s = AdjList[u].size();
    for (i = 0; i < s; i++)
    {
        v = AdjList[u][i];
        if (v != pa)
            dfs(v, u, h + 1);
    }
}
int lgN;
int lca(int u, int v)
{
    if (H[v] > H[u])
        return lca(v, u);
    int i;
    if (H[u] > H[v])
    {
        for (i = lgN - 1; i >= 0; i--)
            if (H[Pa[i][u]] > H[v])
                u = Pa[i][u];
        u = Pa[0][u];
    }
    if (u == v)
        return u;
    for (i = lgN - 1; i >= 0; i--)
    {
        if (Pa[i][u] != Pa[i][v])
        {
            u = Pa[i][u];
            v = Pa[i][v];
        }
    }
    return Pa[0][u];
}
void dfsMark(int u, int pa)
{
    int i, v, s = AdjList[u].size();
    Vis[u] = 0;
    for (i = 0; i < s; i++)
    {
        v = AdjList[u][i];
        if (v != pa)
        {
            dfsMark(v, u);
            mark[u] += mark[v];
        }
    }
}
int main()
{
    int N, M;
    scanf("%d %d", &N, &M);
    for (lgN = 0; (1 << lgN) <= N; lgN++);
    int i, j, u, v, pu, pv;
    int cnt = 0;
    for (i = 0; i < M && cnt < N - 1; i++)
    {
        scanf("%d %d", &u, &v);
        if ((pu = UF(u)) != (pv = UF(v)))
        {
            AdjList[u].push_back(v);
            AdjList[v].push_back(u);
            p[pu] = pv;
            cnt++;
        }
        else
        {
            Q.push({u, v});
        }
    }
    for (i = 1; i <= N; i++)
        if (!Vis[i])
            dfs(i, 0, 0);
    for (j = 1; j < lgN; j++)
    {
        for (i = 1; i <= N; i++)
        {
            Pa[j][i] = Pa[j - 1][Pa[j - 1][i]];
        }
    }
    while (!Q.empty())
    {
        u = Q.front().first;
        v = Q.front().second;
        Q.pop();
        // printf("Q u%d v%d\n", u, v);
        mark[u]++;
        mark[v]++;
        // printf("lca %d\n", lca(u, v));
        mark[lca(u, v)] -= 2;
    }
    for (; i < M; i++)
    {
        scanf("%d %d", &u, &v);
        // printf("# u%d v%d\n", u, v);
        mark[u]++;
        mark[v]++;
        // printf("lca %d\n", lca(u, v));
        mark[lca(u, v)] -= 2;
    }
    for (i = 1; i <= N; i++)
        if (Vis[i])
            dfsMark(i, 0);
    for (i = 1; i <= N; i++)
    {
        // printf("mark[%d] = %d\n", i, mark[i]);
        if (mark[i] == 0 && Pa[0][i] != 0)
            printf("%d %d\n", i, Pa[0][i]);
    }
}

Compilation message (stderr)

pipes.cpp: In function 'int main()':
pipes.cpp:71:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d %d", &N, &M);
     ~~~~~^~~~~~~~~~~~~~~~~
pipes.cpp:77:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d %d", &u, &v);
         ~~~~~^~~~~~~~~~~~~~~~~
pipes.cpp:113:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d %d", &u, &v);
         ~~~~~^~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 10
• Subtask 2: 0 / 10
• Subtask 3: 0 / 10
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• Subtask 10: 0 / 10