Submission #1026968

#	Submission time	Handle	Problem	Language	Result	Execution time	Memory
1026968	2024-07-18T15:47:29 Z	vjudge1	Pipes (CEOI15_pipes)	C++17	Compilation error	0 ms	0 KB

pipes

#include <bits/stdc++.h>

#define ll long long
using namespace std;
const int N = 1e5;
vector < int > adj[N + 2];
struct dsu{
    int par[N + 2];
    int find_par(int &u){
        if(par[u] < 0)return u;
        par[u] = find_par(par[u]);
        return par[u];
    }
    bool union_set(int u , int v){
        u = find_par(u);
        v = find_par(v);
        if(u != v){
            if(par[u] > par[v])swap(u , v);
            par[u] += par[v];
            par[v] = u;
            return true;
        }
        return false;
    }

} par1 , par2;
int timer = 0;
void dfs(int &u , int &p){
    par1.par[u] = par2.par[u] = ++timer;
    for(int v:adj[u]){
        if(v == p) continue;
        if(!par2.par[v]){
            dfs(v , u);
            par1.par[u] = min(par1.par[u] , par1.par[v]);
            if(par1.par[v] == par2.par[v]) cout << u << " " << v <<'\n';
        }
        else par1.par[u] = min(par1.par[u] , par2.par[v]);

    }
}
void solve() {
    int n , m;
    cin >> n >> m;
    memset(par1.par , -1 , sizeof(par1.par));
    memset(par2.par , -1 , sizeof(par2.par));
    for(int i = 1; i <= m ;i ++){
        int u , v;
        cin >> u >> v;
        if(par1.union_set(u , v)){
            adj[u].push_back(v);
            adj[v].push_back(u);
        }
        else if(par2.union_set(u , v)){
            adj[u].push_back(v);
            adj[v].push_back(u);
        }
    }
    memset(par1.par , 0 , sizeof(par1.par));
    memset(par2.par , 0 , sizeof(par2.par));
    for(int i = 1; i <= n ; i++){
        if(!par2.par[i])dfs(i , 0);
    }
    
}

signed main() {
    ios::sync_with_stdio(0), cin.tie(0);
    
    #define _ "maxseq."
    if (fopen(_ "inp", "r")) {
        freopen(_ "inp", "r", stdin);
        freopen(_ "out", "w", stdout);
    }
    
    solve();
}

Compilation message

pipes.cpp: In function 'void solve()':
pipes.cpp:61:33: error: cannot bind non-const lvalue reference of type 'int&' to an rvalue of type 'int'
   61 |         if(!par2.par[i])dfs(i , 0);
      |                                 ^
pipes.cpp:28:24: note:   initializing argument 2 of 'void dfs(int&, int&)'
   28 | void dfs(int &u , int &p){
      |                   ~~~~~^
pipes.cpp: In function 'int main()':
pipes.cpp:71:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   71 |         freopen(_ "inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~
pipes.cpp:72:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   72 |         freopen(_ "out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~