제출 #931739

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
931739		LucaIlie	Star Trek (CEOI20_startrek)	C++17	23 / 100	1018 ms	18768 KiB

startrek

#include <bits/stdc++.h>

using namespace std;

const int MAX_N = 1e5;
const int MAX_D = 1e5;
const int MOD = 1e9 + 7;
bool canWin[MAX_N + 1];
int countChildrenLosers[MAX_N + 1], add[MAX_N + 1], reach[MAX_N + 1], dp[MAX_D][3];
vector<int> adj[MAX_N + 1];

void dfsGame( int u, int p ) {
    canWin[u] = false;
    countChildrenLosers[u] = 0;
    for ( int v: adj[u] ) {
        if ( v == p )
            continue;
        dfsGame( v, u );
        canWin[u] |= (!canWin[v]);
        countChildrenLosers[u] += (!canWin[v]);
    }
}

void dfsCalcAdd( int u, int p ) {
    if ( p == 0 ) {
        add[u] = (canWin[u] ? -1 : 1);
        reach[u] = u;
    } else {
        if ( canWin[u] ) {
            if ( canWin[p] ) {
                add[u] = -1;
                reach[u] = u;
            } else {
                add[u] = add[p] - 1;
                reach[u] = reach[p];
            }
        } else {
            if ( countChildrenLosers[p] >= 2 ) {
                add[u] = 1;
                reach[u] = u;
            } else {
                add[u] = add[p] + 1;
                reach[u] = reach[p];
            }
        }
    }

    for ( int v: adj[u] ) {
        if ( v == p )
            continue;
        dfsCalcAdd( v, u );
    }
}

int main() {
    int n, d;

    cin >> n >> d;
    for ( int i = 0; i < n - 1; i++ ) {
        int u, v;
        cin >> u >> v;
        adj[u].push_back( v );
        adj[v].push_back( u );
        adj[u + n].push_back( v + n );
        adj[v + n].push_back( u + n );
    }

    /*int ans = 0;
    for ( int u = 1; u <= n; u++ ) {
        for ( int v = n + 1; v <= 2 * n; v++ ) {
            adj[u].push_back( v );
            adj[v].push_back( u );
            dfsGame( 1, 0 );
            if ( canWin[1] ) {
                ans++;
                printf( "%d %d\n", u, v - n );
            }
            adj[u].pop_back();
            adj[v].pop_back();
        }
    }
    cout << ans;*/

    int winners = 0;
    for ( int v = 1; v <= n; v++ ) {
        dfsGame( v, 0 );
        winners += canWin[v];
    }

    dfsGame( 1, 0 );
    dfsCalcAdd( 1, 0 );

    for ( int v = 1; v <= n; v++ ) {
        //printf( "%d: %d %d %d\n", v, canWin[v], add[v], reach[v] );
    }

    int ans = 0;
    for ( int v = 1; v <= n; v++ ) {
        if ( canWin[1] ) {
            if ( canWin[v] )
                ans = (ans + n) % MOD;
            else {
                ans = (ans + winners) % MOD;
                if ( reach[v] != 1 )
                    ans = (ans + n - winners) % MOD;
            }
        } else {
            if ( !canWin[v] ) {
                if ( reach[v] == 1 )
                    ans = (ans + n - winners) % MOD;
            }
        }
    }

    cout << ans << "\n";

    return 0;
}

• Subtask 1: 0 / 0
• Subtask 2: 0 / 7
• Subtask 3: 8 / 8
• Subtask 4: 15 / 15
• Subtask 5: 0 / 15
• Subtask 6: 0 / 20
• Subtask 7: 0 / 20
• Subtask 8: 0 / 15