Submission #1028124

#	Time	Username	Problem	Language	Result	Execution time	Memory
1028124		qwewq	Pipes (CEOI15_pipes)	C++14	Compilation error	0 ms	0 KiB

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(const 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; 
int n , m;
void dfs(int &c, int depth, int &par){
	par1.par[c] = depth;
	par2.par[c] = par1.par[c];
	int op = par;
	for (int i : adj[c]){
		if (i == par){ continue;}
		if (par1.par[i] != -1){ par2.par[c] = min( par2.par[c] ,par1.par[i]); continue;}
		dfs(i,depth+1,c);
		par2.par[c] = min(par2.par[c] , par2.par[i]);
	}
	if (par2.par[c]  >= depth && op != -1) cout << c << " " << op << '\n';
}
 
void solve() {
  
    cin >> n >> m;
    for(int i = 1; i <= n; i++){
        par1.par[i] = par2.par[i] = -1;
    }
    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);
         //   cout << u << ' ' <<  v<< '\n';
        }
        else if(par2.union_set(u , v)){
            adj[u].push_back(v);
            adj[v].push_back(u);
          //  cout << u << ' '<< v << '\n';
        }
    }
    for(int  i = 1; i <= n ; i ++){
        par1.par[i] = par2.par[i] = -1;
    }
    for(int i = 1; i <= n ; i++){
        if(par1.par[i] == -1)dfs(i , 0 , -1);
    }
    
}

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 (stderr)

pipes.cpp: In function 'void solve()':
pipes.cpp:66:42: error: cannot bind non-const lvalue reference of type 'int&' to an rvalue of type 'int'
   66 |         if(par1.par[i] == -1)dfs(i , 0 , -1);
      |                                          ^~
pipes.cpp:29:34: note:   initializing argument 3 of 'void dfs(int&, int, int&)'
   29 | void dfs(int &c, int depth, int &par){
      |                             ~~~~~^~~
pipes.cpp: In function 'int main()':
pipes.cpp:76:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   76 |         freopen(_ "inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~
pipes.cpp:77:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   77 |         freopen(_ "out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~