oj.uz

Submission #470218

# Submission time Handle Problem Language Result Execution time Memory
470218 2021-09-03T09:38:09 Z radal LOSTIKS (INOI20_lostiks) C++14
0 / 100
 505 ms 98112 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];
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;
    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;
    rep(i,1,cnt+1){
        din2[i] = din[i];
        if (!din[i]){
            q.push(i);
            st.push(i);
        }
    }
    din2[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);
        }
    }
    int v = s,p = 0;
    ll ans = 0,ans2 = 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++;
    }
    cout << min(ans,ans2);
}

Subtask #1
0 / 23.0

# Verdict Execution time Memory Grader output
1 Correct 33 ms 54348 KB Output is correct
2 Correct 31 ms 54352 KB Output is correct
3 Correct 434 ms 90092 KB Output is correct
4 Correct 470 ms 90984 KB Output is correct
5 Correct 417 ms 91000 KB Output is correct
6 Correct 402 ms 89640 KB Output is correct
7 Correct 431 ms 92884 KB Output is correct
8 Correct 439 ms 93048 KB Output is correct
9 Correct 505 ms 93012 KB Output is correct
10 Correct 427 ms 92308 KB Output is correct
11 Correct 425 ms 92952 KB Output is correct
12 Correct 411 ms 90320 KB Output is correct
13 Correct 407 ms 91896 KB Output is correct
14 Correct 464 ms 90652 KB Output is correct
15 Correct 455 ms 82876 KB Output is correct
16 Correct 482 ms 95820 KB Output is correct
17 Correct 458 ms 93832 KB Output is correct
18 Correct 483 ms 94920 KB Output is correct
19 Correct 457 ms 98112 KB Output is correct
20 Correct 445 ms 96548 KB Output is correct
21 Correct 480 ms 97588 KB Output is correct
22 Correct 30 ms 54348 KB Output is correct
23 Incorrect 30 ms 54388 KB Output isn't correct
24 Halted 0 ms 0 KB -

Subtask #2
0 / 36.0

# Verdict Execution time Memory Grader output
1 Correct 30 ms 54308 KB Output is correct
2 Correct 31 ms 54300 KB Output is correct
3 Correct 37 ms 54404 KB Output is correct
4 Incorrect 36 ms 54340 KB Output isn't correct
5 Halted 0 ms 0 KB -

Subtask #3
0 / 41.0

# Verdict Execution time Memory Grader output
1 Correct 33 ms 54348 KB Output is correct
2 Correct 31 ms 54352 KB Output is correct
3 Correct 434 ms 90092 KB Output is correct
4 Correct 470 ms 90984 KB Output is correct
5 Correct 417 ms 91000 KB Output is correct
6 Correct 402 ms 89640 KB Output is correct
7 Correct 431 ms 92884 KB Output is correct
8 Correct 439 ms 93048 KB Output is correct
9 Correct 505 ms 93012 KB Output is correct
10 Correct 427 ms 92308 KB Output is correct
11 Correct 425 ms 92952 KB Output is correct
12 Correct 411 ms 90320 KB Output is correct
13 Correct 407 ms 91896 KB Output is correct
14 Correct 464 ms 90652 KB Output is correct
15 Correct 455 ms 82876 KB Output is correct
16 Correct 482 ms 95820 KB Output is correct
17 Correct 458 ms 93832 KB Output is correct
18 Correct 483 ms 94920 KB Output is correct
19 Correct 457 ms 98112 KB Output is correct
20 Correct 445 ms 96548 KB Output is correct
21 Correct 480 ms 97588 KB Output is correct
22 Correct 30 ms 54348 KB Output is correct
23 Incorrect 30 ms 54388 KB Output isn't correct
24 Halted 0 ms 0 KB -