Submission #706726

#	Time	Username	Problem	Language	Result	Execution time	Memory
706726		finn__	Pipes (CEOI15_pipes)	C++17	0 / 100	1266 ms	65536 KiB

pipes

#include <bits/stdc++.h>
using namespace std;

struct Dsu
{
    vector<int> p;

    Dsu(size_t n) { p = vector<int>(n, -1); }

    int repr(int u) { return p[u] < 0 ? u : p[u] = repr(p[u]); }

    bool merge(int i, int j)
    {
        i = repr(i);
        j = repr(j);
        if (i == j)
            return 0;

        if (p[i] > p[j])
            swap(i, j);
        p[i] += p[j];
        p[j] = i;
        return 1;
    }

    bool same_set(int i, int j) { return repr(i) == repr(j); }

    int set_size(int i) { return -p[repr(i)]; }
};

constexpr size_t N = 200000;

unsigned y[N][2];

int compare_edges(void const *const a, void const *const b)
{
    unsigned u = *(unsigned *)(a), v = *(unsigned *)(b);
    return u == v ? 0 : (u < v ? -1 : 1);
}

int main()
{
    size_t n, m, l = 0;
    scanf("%zu %zu", &n, &m);

    Dsu d1(n), d2(n);

    while (m--)
    {
        unsigned u, v;
        scanf("%u %u", &u, &v);
        u--, v--;
        if (d1.same_set(u, v))
            d2.merge(u, v);
        else
        {
            d1.merge(u, v);
            y[l][0] = u;
            y[l][1] = v;
            l++;
            y[l][0] = v;
            y[l][1] = 1;
            l++;
        }
    }

    qsort(y, l, sizeof *y, compare_edges);
    for (size_t i = 0; i < l; i++)
        for (size_t j = i + 1; j < l && y[j][0] == y[i][0]; j++)
            if (d2.same_set(y[i][1], y[j][1]))
                d2.merge(y[i][0], y[i][1]);
    for (size_t i = 0; i < l; i++)
        if (!d2.same_set(y[i][0], y[i][1]) && y[i][0] < y[i][1])
            printf("%u %u\n", y[i][0] + 1, y[i][1] + 1);
}

Compilation message (stderr)

pipes.cpp: In function 'int main()':
pipes.cpp:44:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   44 |     scanf("%zu %zu", &n, &m);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~
pipes.cpp:51:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   51 |         scanf("%u %u", &u, &v);
      |         ~~~~~^~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 10
• Subtask 2: 0 / 10
• Subtask 3: 0 / 10
• Subtask 4: 0 / 10
• Subtask 5: 0 / 10
• Subtask 6: 0 / 10
• Subtask 7: 0 / 10
• Subtask 8: 0 / 10
• Subtask 9: 0 / 10
• Subtask 10: 0 / 10