Submission #245392

#	Time	Username	Problem	Language	Result	Execution time	Memory
245392		lyc	Pipes (CEOI15_pipes)	C++14	100 / 100	1845 ms	16292 KiB

pipes

#include <stdio.h>
#include <vector>
using namespace std;

#define TRACE(x) cerr << #x << " :: " << x << endl
#define _ << " " <<
#define SZ(x) (int)(x).size()
#define ALL(x) (x).begin(),(x).end()
#define FOR(i,a,b) for(int i=(a);i<=(b);++i)
#define RFOR(i,a,b) for (int i=(a);i>=(b);--i)

const int mxN = 1e5+5;
int N, M;
int E[2*mxN], ne;
vector<int> al[mxN];

struct UFDS {
    int p[mxN], s[mxN];
    UFDS() { FOR(i,1,N) p[i] = i, s[i] = 1; }
    int finds(int i) { return (p[i] == i) ? i : (p[i] = finds(p[i])); }
    bool unions(int i, int j) {
        int x = finds(i), y = finds(j);
        if (x == y) return 0;
        if (s[x] < s[y]) swap(x,y);
        p[y] = x, s[x] += s[y];
        return 1;
    }
};

int num[mxN], low[mxN], cnt;
void dfs(int u, int p) {
    num[u] = low[u] = cnt++;
    for (int e : al[u]) {
        if (e == p) continue;
        int v = E[e]^u;
        if (num[v] == -1) {
            dfs(v,e);
            low[u] = min(low[u],low[v]);
            if (low[v] > num[u]) printf("%d %d\n", u, v);
        } else low[u] = min(low[u],num[v]);
    }
}

int main() {
    scanf("%d %d", &N, &M);
    UFDS UF[2];
    ne = 0;
    FOR(i,1,M){
        int U, V; scanf("%d %d", &U, &V);
        FOR(j,0,1){
            if (UF[j].unions(U,V)) {
                al[U].push_back(ne);
                al[V].push_back(ne);
                E[ne++] = U^V;
                break;
            }
        }
    }

    FOR(i,1,N) num[i] = -1;
    cnt = 0;
    FOR(i,1,N) if (num[i] == -1) dfs(i,-1);
}

Compilation message (stderr)

pipes.cpp: In function 'int main()':
pipes.cpp:45:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d %d", &N, &M);
     ~~~~~^~~~~~~~~~~~~~~~~
pipes.cpp:49:24: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         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