Submission #379884

#	Time	Username	Problem	Language	Result	Execution time	Memory
379884		parsabahrami	Pipes (CEOI15_pipes)	C++17	100 / 100	4198 ms	13468 KiB

pipes

// To Hell and Back
#include <bits/stdc++.h>
 
using namespace std;

typedef long long int ll;
typedef pair<int, int> pii;
 
#define SZ(x)                       (int) x.size()
#define F                           first
#define S                           second

const int N = 1e5 + 10;
int ps[N], rt[N], S[N], from[N], to[N], P[9][N], H[N], n, m; 
vector<int> adj[N]; vector<pii> vec;

int Find(int v) {
    return !rt[v] ? v : rt[v] = Find(rt[v]);
}

int LCA(int u, int v) {
    if (H[u] < H[v]) swap(u, v);
    for (int i = H[u] - H[v], j = 0; i; i /= 5, j++) {
        while (i % 5) u = P[j][u], i--;
    }
    if (u == v) return u;
    for (int i = 8; ~i; i--) {
        for (int j = 0; j < 4; j++)
            if (P[i][u] != P[i][v])
                u = P[i][u], v = P[i][v];
    }
    return P[0][v];
}

void upd(int v, int p) {
    P[0][v] = p; H[v] = H[p] + 1;
    for (int i = 1; i < 9; i++) {
        P[i][v] = P[i - 1][P[i - 1][P[i - 1][P[i - 1][P[i - 1][v]]]]];
    }	
    for (int u : adj[v]) 
        if (u != p) upd(u, v);
}

void DFS(int v, int p = -1) {
    for (int u : adj[v]) 
        if (u != p) {
            DFS(u, v), ps[v] += ps[u];
            if (ps[u]) vec.push_back({min(u, v), max(u, v)});
            ps[u] = 0;
        }
}

void Union(int u, int v) {
    int pu = Find(u), pv = Find(v);
    if (pu == pv) {
        ps[u]++, ps[v]++, ps[LCA(u, v)] -= 2;
    } else {
        if (S[pv] < S[pu]) swap(pu, pv), swap(u, v);
        S[pv] += S[pu]; rt[pu] = pv;
        DFS(pu), ps[pu] = 0;
        adj[u].push_back(v), adj[v].push_back(u);
        upd(u, v);
    }
}

int main() {
    fill(S, S + N, 1);
    scanf("%d%d", &n, &m);
    for (int i = 1; i <= m; i++) {
        int u, v; scanf("%d%d", &u, &v);
        Union(u, v);
    }
    DFS(Find(1)); sort(vec.begin(), vec.end());
    for (int i = 1; i <= n; i++) {
        for (int u : adj[i]) { 
            if (u < i) continue;
            auto it = lower_bound(vec.begin(), vec.end(), pii(i, u));
            if (it != vec.end() && *it == pii(i, u)) continue;
            printf("%d %d\n", i, u);
        }
    }
    return 0;
}

Compilation message (stderr)

pipes.cpp: In function 'int main()':
pipes.cpp:68:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   68 |     scanf("%d%d", &n, &m);
      |     ~~~~~^~~~~~~~~~~~~~~~
pipes.cpp:70:24: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   70 |         int u, v; scanf("%d%d", &u, &v);
      |                   ~~~~~^~~~~~~~~~~~~~~~

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