Submission #54979

#	Time	Username	Problem	Language	Result	Execution time	Memory
54979		kdh9949	Pipes (CEOI15_pipes)	C++17	100 / 100	1515 ms	8056 KiB

pipes

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

const int N = 100001, H = 17;

int n, m, p[N], P[N], c[N], d[N], s[N];
vector<int> e[N];

int f(int x){ return p[x] = (x == p[x] ? x : f(p[x])); }
int F(int x){ return P[x] = (x == P[x] ? x : F(P[x])); }

void g(int x, int y, int z){
    for(int i : e[x]) if(i != y) g(i, x, z + 1);
    if(s[x] != y && x != f(x)) P[s[x]] = (P[x] == x ? s[x] : x);
    d[x] = z; s[x] = y;
}

int main(){
    scanf("%d%d", &n, &m);
    iota(p, p + n + 1, 0);
    iota(P, P + n + 1, 0);
    iota(s, s + n + 1, 0);
    fill(c + 1, c + n + 1, 1);
    for(int x, y; m--; ){
        scanf("%d%d", &x, &y);
        if(f(x) != f(y)){
            if(c[f(x)] < c[f(y)]) swap(x, y);
            g(y, x, d[x] + 1); P[y] = y;
            e[x].push_back(y); e[y].push_back(x);
            c[f(x)] += c[f(y)]; p[f(y)] = f(x);
        }
        else{
            x = F(x); y = F(y);
            while(x != y){
                if(d[x] > d[y]){ P[x] = F(P[s[x]]); x = F(x); }
                else{ P[y] = F(P[s[y]]); y = F(y); }
            }
        }
    }
    for(int i = 1; i <= n; i++) if(P[i] == i && s[i] != i) printf("%d %d\n", i, s[i]);
}

Compilation message (stderr)

pipes.cpp: In function 'int main()':
pipes.cpp:19:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d", &n, &m);
     ~~~~~^~~~~~~~~~~~~~~~
pipes.cpp:25:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d%d", &x, &y);
         ~~~~~^~~~~~~~~~~~~~~~

• 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