#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define mp make_pair
#define pb push_back
#define x first
#define y second
#define pii pair<int, int>
#define p3i pair<pii, int>
#define pll pair<ll, ll>
#define p3l pair<pll, ll>
#define lseg L, (L+R)/2, N*2+1
#define rseg (L+R)/2+1, R, N*2+2
#define ub upper_bound
#define lb lower_bound
#define pq priority_queue
#define MN 1000000007
#define fox(k, x) for (int k=0; k<x; ++k)
#define fox1(k, x) for (int k=1; k<=x; ++k)
#define foxr(k, x) for (int k=x-1; k>=0; --k)
#define fox1r(k, x) for (int k=x; k>0; --k)
#define ms multiset
#define flood(x) memset(x, 0x3f3f3f3f, sizeof x)
#define drain(x) memset(x, 0, sizeof x)
#define rng() (rand() >> 3)*rand()
#define scan(x) do{while((x=getchar())<'0'); for(x-='0'; '0'<=(_=getchar()); x=(x<<3)+(x<<1)+_-'0');}while(0)
char _;
int n, m, t, a, b, X2, Y2, P,
r[100001], p[100001], h[100001], d[100001];
bool u[100001];
vector<int> com[100001];
bool mrg(int A, int B){
if (A==B) return 0;
if (com[A].size()<com[B].size()) return mrg(B, A);
for (auto i:com[B]){
com[A].pb(i);
r[i]=A;
}
return 1;
}
void dfs(int N, int P){
if ((p[N]=P)>0) d[N]=d[P]+1;
fox(l, com[N].size()){
if (com[N][l]==P) continue;
dfs(com[N][l], N);
}
}
void lca(int X, int Y){
X=r[X]; Y=r[Y];
while(X!=Y){
if (d[X2=h[X]]>d[Y2=h[Y]]){
u[X2]=1;
t=h[r[p[X2]]];
mrg(X, r[p[X2]]);
h[X]=t;
} else {
u[Y2]=1;
t=h[r[p[Y2]]];
mrg(Y, r[p[Y2]]);
h[Y]=t;
}
X=r[X]; Y=r[Y];
}
}
int q[100001];
int main(){
scan(n); scan(m);
fox1(l, n){
r[l]=l;
com[l].clear(); com[l].pb(l);
}
fox(l, m){
scan(a); scan(b);
if (mrg(r[a], r[b])){
//cout << l << endl;
h[P]=a;
d[P]=b;
q[P++]=l;
}
}
fox1(l, n){
com[l].clear();
}
fox(l, P){
com[h[l]].pb(d[l]);
com[d[l]].pb(h[l]);
}
fox1(l, n){
if (p[l]==0){
dfs(l, -1);
}
}
fox1(l, n){
r[l]=l; h[l]=l;
com[l].clear(); com[l].pb(l);
}
P=0;
rewind(stdin);
scan(n); scan(m);
fox(l, m){
scan(a); scan(b);
(l==q[P]) ? ++P : lca(a, b);
}
fox1(l, n){
if (!u[l] && p[l]>0){
printf("%i %i\n", l, p[l]);
}
}
return 0;
}
Compilation message
pipes.cpp: In function 'void dfs(int, int)':
pipes.cpp:18:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
#define fox(k, x) for (int k=0; k<x; ++k)
pipes.cpp:45:9:
fox(l, com[N].size()){
~~~~~~~~~~~~~~~~
pipes.cpp:45:5: note: in expansion of macro 'fox'
fox(l, com[N].size()){
^~~
pipes.cpp: In function 'int main()':
pipes.cpp:104:21: error: third operand to the conditional operator is of type 'void', but the second operand is neither a throw-expression nor of type 'void'
(l==q[P]) ? ++P : lca(a, b);
^~~
