oj.uz

Submission #470221

# Submission time Handle Problem Language Result Execution time Memory
470221 2021-09-03T09:43:26 Z radal LOSTIKS (INOI20_lostiks) C++14
0 / 100
 486 ms 96796 KB 
#include <bits/stdc++.h>
#define rep(i,l,r) for (int i = l; i < r; i++)
#define repr(i,r,l) for (int i = r; i >= l; i--)
#define pb push_back
#define debug(x) cerr << #x <<  " : " << x << endl;
#define X first
#define Y second
using namespace std;

typedef long long ll;
typedef pair<int,int> pll;

const ll N = 1e5+20,mod = 1e9+7;
int poww(int a,int k){
    if (!k) return 1;
    if (k == 1) return a;
    int r = poww(a,k/2);
    return 1ll*r*r%mod*poww(a,k&1)%mod;
}
int n,s,t;
vector<pll> adj[N];
int k[22],din[22],par[N][20],h[N],mark[N],din2[N],din3[N];
vector<int> dp[N][22],out[22];
pll e[22];
bitset<N> vis;
void bfs(int v){
    queue<int> q;
    q.push(k[v]);
    vis[k[v]] = 1;
    while (!q.empty()){
        int u = q.front();
        q.pop();
        for (pll w : adj[u]){
            if (vis[w.X]) continue;
            vis[w.X] = 1;
            q.push(w.X);
            for (int x : dp[u][v])
                dp[w.X][v].pb(x);
            if (w.Y)
                dp[w.X][v].pb(w.Y);
            if (u == t && v != 21) dp[w.X][v].pb(21);
        }
    }
    vis.reset();
}
bool pre(int v){
    mark[v] = 1;
    din[v] = 0;
    for (int u : dp[s][v]){
        din[v]++;
        out[u].pb(v);
        if (mark[u] == 1)
            return 0;
        if (mark[u] == 2) continue;
        if (!pre(u)) return 0;
    }
    for(int u : dp[e[v].X][v]){
        if (u != v){
            out[u].pb(v);
            din[v]++;
            if (mark[u] == 1) return 0;
            if (!mark[u] && !pre(u)) return 0;
        }
    }
    for(int u : dp[e[v].Y][v]){
        if (u != v){
            out[u].pb(v);
            din[v]++;
            if (mark[u] == 1) return 0;
            if (!mark[u] && !pre(u)) return 0;
        }
    }
    mark[v] = 2;
    return 1;
}
void dfs(int v,int p){
    for (pll u : adj[v]){
        if (u.X == p) continue;
        h[u.X] = h[v]+1;
        par[u.X][0] = v;
        dfs(u.X,v);
    }
}
inline int lca(int u,int v){
    if (h[u] > h[v]) swap(u,v);
    repr(i,18,0)
        if (h[v]-h[u] >= (1 << i))
            v = par[v][i];
    if (u == v) return u;
    repr(i,18,0){
        if (par[v][i] != par[u][i]){
            v = par[v][i];
            u = par[u][i];
        }
    }
    return par[v][0];
}
inline int dist(int u,int v){
    int w = lca(u,v);
    return h[v]+h[u]-2*h[w];
}
int main(){
    ios :: sync_with_stdio(0); cin.tie(0); cout.tie(0);
    memset(din,-1,sizeof din);
    int cnt = 0;
    cin >> n >> s >> t;
    rep(i,1,n){
        int u,v,w;
        cin >> u >> v >> w;
        if (!w){
            adj[u].pb({v,0});
            adj[v].pb({u,0});
        }
        else{
            cnt++;
            k[cnt] = w;
            e[cnt] = {u,v};
            adj[u].pb({v,cnt});
            adj[v].pb({u,cnt});
        }
    }
    k[21] = t;
    rep(i,1,cnt+1) bfs(i);
    bfs(21);
    e[21] = {t,t};
    if (!pre(21)){
        cout << -1;
        return 0;
    }
    vector<int> ve,ve2,ve3;
    dfs(1,-1);
    rep(j,1,19){
        rep(i,2,n+1){
            if (h[i] < (1 << j)) continue;
            par[i][j] = par[par[i][j-1]][j-1];
        }
    }
    if (!din[21]){
        cout << dist(s,t);
        return 0;
    }
    queue<int> q;
    stack<int> st;
    priority_queue<pll> pq;
    rep(i,1,cnt+1){
        din2[i] = din3[i] = din[i];
        if (!din[i]){
            q.push(i);
            st.push(i);
            pq.push({dist(k[i],t),i});
        }
    }
    din2[21] = din3[21] = din[21];
    while (!q.empty()){
        int v = q.front();
        q.pop();
        ve.pb(v);
        for (int u : out[v]){
            din[u]--;
            if (!din[u]) q.push(u);
        }
    }
    while (!st.empty()){
        int v = st.top();
        st.pop();
        ve2.pb(v);
        for (int u : out[v]){
            din2[u]--;
            if (!din2[u]) st.push(u);
        }
    }
    while (!pq.empty()){
        int v = pq.top().Y;
        pq.pop();
        ve3.pb(v);
        for (int u : out[v]){
            din3[u]--;
            if (!din3[u]) pq.push({dist(t,k[u]),u});
        }
    }
    int v = s,p = 0;
    ll ans = 0,ans2 = 0,ans3 = 0;
    while (v != t){
        int u = ve[p];
        if (u == 21){
            ans += dist(v,t);
            break;
        }
        ans += dist(v,k[u]);
        int w1 = dist(k[u],e[u].X),w2 = dist(k[u],e[u].Y);
        if (w1 <= w2){
            v = e[u].X;
            ans += w1;
        }
        else{
            v = e[u].Y;
            ans+=w2;
        }
        p++;
    }
    v = s,p = 0;
    while (v != t){
        int u = ve2[p];
        if (u == 21){
            ans2 += dist(v,t);
            break;
        }
        ans2 += dist(v,k[u]);
        int w1 = dist(k[u],e[u].X),w2 = dist(k[u],e[u].Y);
        if (w1 <= w2){
            v = e[u].X;
            ans2 += w1;
        }
        else{
            v = e[u].Y;
            ans2 += w2;
        }
        p++;
    }
    v = s, p = 0;
    while (v != t){
        int u = ve3[p];
        if (u == 21){
            ans3 += dist(v,t);
            break;
        }
        ans3 += dist(v,k[u]);
        int w1 = dist(k[u],e[u].X),w2 = dist(k[u],e[u].Y);
        if (w1 <= w2){
            v = e[u].X;
            ans3 += w1;
        }
        else{
            v = e[u].Y;
            ans3 += w2;
        }
        p++;
    }
    cout << min({ans3,ans,ans2});
}

Subtask #1
0 / 23.0

# Verdict Execution time Memory Grader output
1 Correct 30 ms 54340 KB Output is correct
2 Correct 31 ms 54280 KB Output is correct
3 Correct 434 ms 88752 KB Output is correct
4 Correct 407 ms 89564 KB Output is correct
5 Correct 424 ms 89628 KB Output is correct
6 Correct 405 ms 88360 KB Output is correct
7 Correct 427 ms 91504 KB Output is correct
8 Correct 481 ms 91740 KB Output is correct
9 Correct 435 ms 91676 KB Output is correct
10 Correct 426 ms 91092 KB Output is correct
11 Correct 486 ms 91416 KB Output is correct
12 Correct 427 ms 88872 KB Output is correct
13 Correct 465 ms 90564 KB Output is correct
14 Correct 428 ms 89224 KB Output is correct
15 Correct 403 ms 81524 KB Output is correct
16 Correct 467 ms 94416 KB Output is correct
17 Correct 417 ms 92496 KB Output is correct
18 Correct 441 ms 93664 KB Output is correct
19 Correct 440 ms 96796 KB Output is correct
20 Correct 435 ms 95204 KB Output is correct
21 Correct 435 ms 96168 KB Output is correct
22 Correct 31 ms 54348 KB Output is correct
23 Correct 35 ms 54360 KB Output is correct
24 Incorrect 28 ms 54384 KB Output isn't correct
25 Halted 0 ms 0 KB -

Subtask #2
0 / 36.0

# Verdict Execution time Memory Grader output
1 Correct 31 ms 54312 KB Output is correct
2 Correct 30 ms 54376 KB Output is correct
3 Correct 30 ms 54428 KB Output is correct
4 Incorrect 30 ms 54316 KB Output isn't correct
5 Halted 0 ms 0 KB -

Subtask #3
0 / 41.0

# Verdict Execution time Memory Grader output
1 Correct 30 ms 54340 KB Output is correct
2 Correct 31 ms 54280 KB Output is correct
3 Correct 434 ms 88752 KB Output is correct
4 Correct 407 ms 89564 KB Output is correct
5 Correct 424 ms 89628 KB Output is correct
6 Correct 405 ms 88360 KB Output is correct
7 Correct 427 ms 91504 KB Output is correct
8 Correct 481 ms 91740 KB Output is correct
9 Correct 435 ms 91676 KB Output is correct
10 Correct 426 ms 91092 KB Output is correct
11 Correct 486 ms 91416 KB Output is correct
12 Correct 427 ms 88872 KB Output is correct
13 Correct 465 ms 90564 KB Output is correct
14 Correct 428 ms 89224 KB Output is correct
15 Correct 403 ms 81524 KB Output is correct
16 Correct 467 ms 94416 KB Output is correct
17 Correct 417 ms 92496 KB Output is correct
18 Correct 441 ms 93664 KB Output is correct
19 Correct 440 ms 96796 KB Output is correct
20 Correct 435 ms 95204 KB Output is correct
21 Correct 435 ms 96168 KB Output is correct
22 Correct 31 ms 54348 KB Output is correct
23 Correct 35 ms 54360 KB Output is correct
24 Incorrect 28 ms 54384 KB Output isn't correct
25 Halted 0 ms 0 KB -