Submission #715136

#	Time	Username	Problem	Language	Result	Execution time	Memory
715136		Pietra	Pictionary (COCI18_pictionary)	C++17	0 / 140	43 ms	65536 KiB

pictionary

#include<bits/stdc++.h>
using namespace std ;

const int maxl = 22 ; 
const int maxn = 2e5 + 5 ; 

int n, q, m ; 
int pai[maxn], sz[maxn], tab[maxl][maxn], nivel[maxn], mx_t[maxl][maxn] ; 
vector<pair<int,int>> grafo[maxn] ; 

struct DSU{

    int find(int a){(pai[a] == a ? a : pai[a] = find(pai[a])) ; }

    void join(int a, int b){
        a = find(a), b = find(b) ; 
        if(a == b) return ; 
        if(sz[a] > sz[b]) swap(a, b) ; 
        sz[b] += sz[a] ; pai[a] = b ; 
    }

} dsu ; 

void dfs(int v, int p){

    tab[0][v] = p ; 

    for(auto a : grafo[v]){
        if(a.first == p || nivel[a.first] != -1) continue ;
        mx_t[0][a.first] = a.second ; 
        nivel[a.first] = nivel[v] + 1 ; 
        dfs(a.first, v) ; 
    }

}

int lca(int a, int b){

    if(nivel[a] > nivel[b]) swap(a, b) ; 

    int ans = 0 ; 

    for(int i = maxl - 1 ; i >= 0 ; i--){
        if(tab[i][b] != -1 && nivel[tab[i][b]] >= nivel[a]){
            ans = max(ans, mx_t[i][b]) ; 
            b = tab[i][b] ; 
        }
    }

    if(a == b) return ans ; 

    for(int i = maxl - 1 ; i >= 0 ; i--){
        if(tab[i][a] != -1 && tab[i][b] != -1 && tab[i][a] != tab[i][b]){
            ans = max({ans, mx_t[i][a], mx_t[i][b]}) ; 
            a = tab[i][a], b = tab[i][b] ;
        }
    }

    return max({ans, mx_t[0][a], mx_t[0][b]}) ;

}

int main(){

    ios_base::sync_with_stdio(false) ; cin.tie(NULL) ; 

    cin >> n >> m >> q ; 

    for(int i = 1 ; i <= n ; i++) nivel[i] = -1, pai[i] = i, sz[i] = 1 ; 

    for(int i = m ; i > 0 ; i--){
        for(int j = i + i ; j <= n ; j += i){
            if(dsu.find(i) == dsu.find(j)) continue ; 
            dsu.join(i, j) ; 
            grafo[i].push_back({j, m-i+1}) ; grafo[j].push_back({i, m-i+1}) ;
        }
    }

    for(int i = 1 ; i < maxl ; i++){
        for(int j = 1 ; j <= n ; j++) tab[i][j] = -1 ; 
    }

    nivel[1] = 0 ; 
    dfs(1, 0) ; 

    for(int i = 1 ; i < maxl ; i++){
        for(int j = 1 ; j <= n ; j++){
            if(tab[i-1][j] == -1) continue ; 
            tab[i][j] = tab[i-1][tab[i-1][j]] ; 
            mx_t[i][j] = max(mx_t[i-1][j], mx_t[i-1][tab[i-1][j]]) ;
        }
    }

    for(int i = 1 ; i <= q ; i++){
        int a, b ; cin >> a >> b ; 
        cout << lca(a, b) << "\n" ;
    }

}

Compilation message (stderr)

pictionary.cpp: In member function 'int DSU::find(int)':
pictionary.cpp:13:65: warning: no return statement in function returning non-void [-Wreturn-type]
   13 |     int find(int a){(pai[a] == a ? a : pai[a] = find(pai[a])) ; }
      |                                                                 ^

• Subtask 1: 0 / 14
• Subtask 2: 0 / 14
• Subtask 3: 0 / 14
• Subtask 4: 0 / 14
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• Subtask 10: 0 / 14