Submission #1208968

#	Time	Username	Problem	Language	Result	Execution time	Memory
1208968		kitkat12	Cat Exercise (JOI23_ho_t4)	C++20	31 / 100	2097 ms	44272 KiB

Main

// Problem URL: https://oj.uz/problem/view/JOI23_ho_t4
// Start Time: 5/27/2025, 9:44:51 PM

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
#define mp make_pair
#define pb push_back
#define F first
#define S second
#define debug(x) std::cout << #x << ": " << x << "\n"
#define all(v) v.begin(), v.end()
#define li(i,a,b) for (int i = a; i < b; i++)
#define endl '\n'
#define mem(name,val) memset(name,val,sizeof(name))
#define max(a,b) max<ll>(a,b)
#define min(a,b) min<ll>(a,b)

const int nmax = 2e5+3;
const int LOG = 32-__builtin_clz(nmax);

vector<int> adj[nmax];
int p[nmax], pos[nmax];
int n;

int t[2*nmax]; // promeni u sparse table jer nema update
void build(){for(int x = n-1; x>0; x--)t[x]=max(t[2*x],t[2*x+1]);}
void update(int i,int v){for(t[i+=n]=v;i>1;i>>=1)t[i>>1]=max(t[i],t[i^1]);}
int get (int l, int r){
    int res = -1;
    for(l+=n,r+=n;l<r;l>>=1,r>>=1){
        if(l&1)res=max(res,t[l++]);
        if(r&1)res=max(res,t[--r]);
    }
    return res;
}

int timer = -1;
int dep[nmax], dt[nmax], ft[nmax], jmp[nmax][LOG+1];
void dfs(int u, int par=-1){
    dt[u]=++timer;
    for(int v : adj[u]){
        if(v==par)continue;
        jmp[v][0]=u;
        dep[v]=dep[u]+1;
        dfs(v,u);
    }
    ft[u]=timer;
}
void prec_lca(){
    for(int j = 1; j<=LOG; j++){
        for(int i = 1; i<=n; i++){
            jmp[i][j] = jmp[jmp[i][j-1]][j-1];
        }
    }
}
int lca(int a, int b){
    if(dep[a]<dep[b])swap(a,b);
    //podigni a na istu visinu kao b
    int dif = dep[a]-dep[b];
    for(int i = 0; i<=LOG; i++){
        if(dif&(1<<i)){
            a = jmp[a][i];
        }
    }
    if(a==b)return a;

    for(int i = LOG; i>=0; i--){
        if(jmp[a][i] != jmp[b][i]){
            a = jmp[a][i];
            b = jmp[b][i];
        }
    }
    return jmp[a][0];
}

bool obst[nmax];

ll maxmoves(int mn){
    ll res = 0;
    obst[mn]=1;
    update(dt[mn],-1);
    // prvo odradi sva podstabla
    for(int v : adj[mn]){
        if(v==jmp[mn][0]) continue;//?
        int maxv = get(dt[v],ft[v]+1);
        if(maxv==-1)continue;
        int maxnode = pos[maxv];
        res = max(res, maxmoves(maxnode) + (dep[maxnode] - dep[mn]));
        // ocrni celo podstablo 
        // zameni sa lazy kasnije 
        if(p[mn]==n) continue;
        li(i,dt[maxnode],ft[maxnode]+1){
            t[i+n]=-1;
        }
        build();
    }

    // nadji poslednjeg ne blokiranog pretka  
    if(p[mn]!=n){
        int maxv = mn;
        while(!obst[jmp[maxv][0]])maxv=jmp[maxv][0];
        if(maxv != mn){
            maxv = get(dt[maxv],ft[maxv]+1);
            if(maxv!=-1){
                int maxnode = pos[maxv];
                res = max(res,maxmoves(maxnode) + dep[maxnode] + dep[mn] - 2*dep[lca(maxnode,mn)]);
            }
        }
    }
    return res;
}

int main() 
{
    ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
    cin>>n;
    li(i,1,n+1){
        cin>>p[i];
        pos[p[i]]=i;
    }
    li(i,0,n-1){
        int a,b;
        cin>>a>>b;
        adj[a].pb(b);
        adj[b].pb(a);
    }
    dfs(pos[n]);
    li(i,1,n+1) t[dt[i]+n]=p[i];
    build();    
    prec_lca();
    cout<<maxmoves(pos[n]);
    return 0;
}

• Subtask 1: 7 / 7
• Subtask 2: 7 / 7
• Subtask 3: 7 / 7
• Subtask 4: 10 / 10
• Subtask 5: 0 / 20
• Subtask 6: 0 / 23
• Subtask 7: 0 / 26