Submission #560079

#	Time	Username	Problem	Language	Result	Execution time	Memory
560079		Huy	Valley (BOI19_valley)	C++17	100 / 100	244 ms	48340 KiB

valley

#include<bits/stdc++.h>
#define int long long
#define pii pair<int,int>
#define fi first
#define se second
/*#pragma GCC target ("avx2")
#pragma GCC optimization ("O3")
#pragma GCC optimization ("unroll-loops")
#pragma GCC optimize("Ofast")
#pragma GCC target("avx,avx2,fma")*/
using namespace std;
using ll = long long;
using ull = unsigned long long;
using ldb = long double;
const int N = (int)5e5;
const int maxN = (int)5e5 + 5;
const ll mod = 1e9 + 7;
//const int mod = 998244353;
const ll infty = 1e17;
const ll logn = 18;
const int base = 311;
const int Block_size = 500;
const int ep = 'a';

int cu[] = {0,0,1,-1};
int cv[] = {-1,1,0,0};

int du[] = {-1,-1,+1,1};
int dv[] = {-1,+1,-1,1};

int cled[] = {6,2,5,5,4,5,6,3,7,6};

void InputFile()
{
    freopen(".inp","r",stdin);
    freopen(".out","w",stdout);
    //freopen("test.out","r",stdin);
}

void FastInput()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
}

int n,s,q,e;
vector<vector<pii>> adj;
int spec[maxN];
int ispec[maxN];
int x[maxN],y[maxN],w[maxN];

void Read()
{
    cin >> n >> s >> q >> e;
    adj.resize(n+1);
    for(int i = 1;i < n;i++)
    {
        cin >> x[i] >> y[i] >> w[i];
        adj[x[i]].push_back({y[i],w[i]});
        adj[y[i]].push_back({x[i],w[i]});
    }
    for(int i = 1;i <= s;i++)
    {
        cin >> spec[i];
        ispec[spec[i]] = 1;
    }
}

int TimeDFS = 0;
int in[maxN];
int jdep[maxN];
int depth[maxN];
int f[30][maxN];
int lca[30][maxN];
int dak[maxN];
int lg[maxN];
int subsz[maxN];

void ScanLog()
{
    lg[1] = 0;
    for(int i = 2;i <= n;i++)
        lg[i] = lg[i/2] + 1;
}

void preDFS(int u,int p)
{
    in[u] = ++TimeDFS;
    subsz[u] = 1;
    if(ispec[u]) dak[u] = 0;
    else dak[u] = infty;
    for(pii x : adj[u])
    {
        if(x.fi == p) continue;
        depth[x.fi] = depth[u] + x.se;
        jdep[x.fi] = jdep[u] + 1;
        preDFS(x.fi,u);
        dak[u] = min(dak[u],dak[x.fi] + x.se);
        subsz[u] += subsz[x.fi];
    }
}

void preDFS2(int u,int p)
{
    for(pii x : adj[u])
    {
        if(x.fi == p) continue;
        lca[0][x.fi] = u;
        f[0][x.fi] = dak[u] - depth[u];
        for(int i = 1;i <= lg[n];i++)
        {
            lca[i][x.fi] = lca[i-1][lca[i-1][x.fi]];
            f[i][x.fi] = min(f[i-1][x.fi],f[i-1][lca[i-1][x.fi]]);
        }
        preDFS2(x.fi,u);
    }
}

int Jump(int u,int p)
{
    int k = jdep[u] - jdep[p];
    int res = dak[u] - depth[u];
    for(int i = lg[n];i >= 0;i--)
    {
        if(k & (1 << i))
        {
            res = min(res,f[i][u]);
            u = lca[i][u];
            k ^= (1 << i);
        }
    }
    return res;
}

void Solve()
{
    ScanLog();
    preDFS(e,0);
    preDFS2(e,0);
    //cout << f[0][3];
    //cout << Jump(5,3);
    while(q--)
    {
        int id,r;
        cin >> id >> r;
        if(jdep[x[id]] < jdep[y[id]]) swap(x[id],y[id]);
        if(in[r] >= in[x[id]] && in[r] <= in[x[id]] + subsz[x[id]] - 1)
        {
            int res = depth[r] + Jump(r,x[id]);
            if(res >= infty) cout <<"oo"<<'\n';
            else cout << res <<'\n';
        }
        else cout <<"escaped"<<'\n';
    }
}

void Debug()
{
    //Main_sub();
    //Naive();
}


int32_t main()
{
    FastInput();
    //InputFile();
    //int sub_type;
    //cin >> sub_type;
    //Sieve();
    int test;
    //cin >> test;
    test = 1;
    while(test--)
        //for(int prc = 1; prc <= test; prc++)
    {
        Read();
        Solve();
        //Debug();
    }
}

Compilation message (stderr)

valley.cpp: In function 'void InputFile()':
valley.cpp:35:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   35 |     freopen(".inp","r",stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~
valley.cpp:36:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   36 |     freopen(".out","w",stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~

• Subtask 1: 9 / 9
• Subtask 2: 27 / 27
• Subtask 3: 23 / 23
• Subtask 4: 41 / 41