Submission #1172413

#	Time	Username	Problem	Language	Result	Execution time	Memory
1172413		DanielPr8	Railway (BOI17_railway)	C++20	0 / 100	68 ms	34096 KiB

railway

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vll = vector<ll>;
using vvl = vector<vll>;
using pll = pair<ll,ll>;
using vpl = vector<pll>;
using vvp = vector<vpl>;
#define f first
#define s second
#define pb push_back
#define all(v) v.begin(),v.end()
vll ans, sz, dt;
vvp g;
ll k;
vvl pr;
void dfs(ll cr){
    for(pll i:g[cr]){
        if(i.f!=pr[0][cr]){
            pr[0][i.f]=cr;
            dt[i.f]=dt[cr]+1;
            dfs(i.f);
        }
    }
}
void calc(ll cr){
    for(pll i:g[cr]){
        if(i.f!=pr[0][cr]){
            pr[0][i.f]=cr;
            sz[cr]+=sz[i.f];
            if(sz[i.f]>=k)ans.pb(i.s);
            calc(i.f);
        }
    }
}
ll fpr(ll a, ll b){
    for(ll h = 20; h >= 0; --h){
        if((1<<h) <= b){
            a = pr[h][a];
            b -= (1<<h);
        }
    }
    return a;
}

ll lca(ll a, ll b){
    if(dt[a]>dt[b])swap(a,b);
    b = fpr(b, dt[b]-dt[a]);
    if(a==b)return a;
    for(ll h = 20; h >= 0; --h){
        if(pr[h][a] != pr[h][b]){
            a = pr[h][a];
            b = pr[h][b];
        }
    }
    return pr[0][a];
}
int main(){
    ios_base::sync_with_stdio(0);cin.tie(NULL);
    ll n, m, a ,b, s;
    cin >> n >> m >> k;
    g = vvp(n);
    for(ll i = 0; i < n-1; ++i){
        cin >> a >> b;
        a--;b--;
        g[a].pb({b,i});
        g[b].pb({a,i});
    }
    pr = vvl(20, vll(n));
    dt = sz = vll(n);
    dfs(0);
    for(ll h = 1; h < 20; ++h){
        for(ll i = 0; i < n; ++i){
            pr[h][i] = pr[h-1][pr[h-1][i]];
        }
    }

    for(ll i = 0; i < m; ++i){
        cin >> s;
        cin >> a >> b;
        a--;b--;
        ll c = lca(a, b);
        sz[a]++;
        sz[b]++;
        sz[c]-=2;
    }
    calc(0);
    cout << ans.size() << "\n";
    for(ll i:ans)cout << i << " ";
}

• Subtask 1: 0 / 8
• Subtask 2: 0 / 15
• Subtask 3: 0 / 7
• Subtask 4: 0 / 29
• Subtask 5: 0 / 16
• Subtask 6: 0 / 25