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## Discussion of Problem 1671. Anansi's Cobweb

WA on 6. Can anyone tell me why?
Posted by raphaelrbr 17 Mar 2019 04:29
#include <bits/stdc++.h>
using namespace std;

#define ll long long
#define F first
#define S second
#define mp make_pair
#define pii pair<int,int>
#define vi vector<int>
#define pq priority_queue
#define pb push_back
#define watch(x) cout << (#x) << " is " << (x) << endl
#define ALL(a) (a.begin()),(a.end())
#define FOR(x,to) for(x=0;x<(to);x++)
#define FORI(a,b) for(int i = a; i<b; i++)
#define fastio ios::sync_with_stdio(0); cin.tie(NULL);
const int INF = 0x3f3f3f3f;

struct ar{
ll x,y;
};

ar v[100100];
int p[100100] = {0};
ll id[100100];
ll sz[100100];
ll num;

ll find(ll x){
if(id[x] == x) return x;
return id[x] = find(id[x]);
}

void join(ll x, ll y){
ll p = find(x);
ll q = find(y);
if(p==q) return;
num--;
if(sz[p] > sz[q]) {
ll t = q; p = q; q = t;
}
id[p] = q;
sz[p] += sz[q];
}

int main(){
fastio
ll n,m,i,q;
cin >> n >> m;
num = n;

ll arf[100100];
ll ans[100100];

FOR(i,m){
cin >> v[i+1].x >> v[i+1].y;
}
FOR(i,m+1){
id[i+1] = i+1;
sz[i+1] = 1;
}
cin >> q;
FOR(i,q){
ll x;
cin >> x;
p[x] = 1;
arf[q-i] = x;
}

FOR(i,m+1){
if(i==0) continue;
if(!p[i]){
join(v[i].x, v[i].y);
}
}

ans[q] = num;
for(int i = 1; i<=q; i++){
join(v[arf[i]].x, v[arf[i]].y);

ans[q-i] = num;

}

for(int i = 1; i<=q; i++){
cout << ans[i] << " ";
}

cout << "\n";

return 0;
}

Edited by author 17.03.2019 04:30