Submission #406873

#	Time	Username	Problem	Language	Result	Execution time	Memory
406873		Ruxandra985	The Xana coup (BOI21_xanadu)	C++14	100 / 100	109 ms	15312 KiB

xanadu

#include <bits/stdc++.h>
#define DIMN 100010
using namespace std;
int dp[DIMN][2][2] , c[DIMN];
vector <int> v[DIMN];

void dfs (int nod , int tt){
    int i , vecin , par , impar , par_ant , ok = 0;

    for (i = 0 ; i < v[nod].size() ; i++){
        vecin = v[nod][i];
        if (vecin != tt){
            dfs(vecin , nod);
            ok = 1;
        }
    }

    if (!ok){ /// e frunza

        dp[nod][c[nod]][0] = 0;
        dp[nod][1 - c[nod]][1] = 1;
        return;

    }

    /// daca eu apas nod, toti vecinii trb sa fie 1

    par = 0;
    impar = DIMN;

    for (i = 0 ; i < v[nod].size() ; i++){
        vecin = v[nod][i];
        if (vecin != tt){


            par_ant = par;
            par = min(par + dp[vecin][1][0] , impar + dp[vecin][1][1]);
            impar = min(impar + dp[vecin][1][0] , par_ant + dp[vecin][1][1]);

        }
    }

    if (c[nod] == 1){
        dp[nod][0][1] = min(dp[nod][0][1] , par + 1);
        dp[nod][1][1] = min (dp[nod][1][1] , impar + 1);
    }
    else { /// c[nod] = 0;
        dp[nod][0][1] = min(dp[nod][0][1] , impar + 1);
        dp[nod][1][1] = min (dp[nod][1][1] , par + 1);
    }

    /// daca nu apas nod, toti vecinii trebuie sa fie 0
    par = 0;
    impar = DIMN;

    for (i = 0 ; i < v[nod].size() ; i++){
        vecin = v[nod][i];
        if (vecin != tt){


            par_ant = par;
            par = min(par + dp[vecin][0][0] , impar + dp[vecin][0][1]);
            impar = min(impar + dp[vecin][0][0] , par_ant + dp[vecin][0][1]);

        }
    }


    if (c[nod] == 1){
        dp[nod][0][0] = min(dp[nod][0][0] , impar);
        dp[nod][1][0] = min (dp[nod][1][0] , par);
    }
    else { /// c[nod] = 0;
        dp[nod][0][0] = min(dp[nod][0][0] , par);
        dp[nod][1][0] = min (dp[nod][1][0] , impar);
    }


}


int main()
{
    FILE *fin = stdin;
    FILE *fout = stdout;
    int n , i , x , y;
    fscanf (fin,"%d",&n);
    for (i = 1 ; i < n ; i++){
        fscanf (fin,"%d%d",&x,&y);
        v[x].push_back(y);
        v[y].push_back(x);
    }
    for (i = 1 ; i <= n ; i++){
        fscanf (fin,"%d",&c[i]);
        dp[i][0][0] = dp[i][0][1] = dp[i][1][0] = dp[i][1][1] = n + 1;
    }

    dfs(1 , 0);

    if (min(dp[1][0][0] , dp[1][0][1]) > n)
        fprintf (fout,"impossible");
    else fprintf (fout,"%d",min(dp[1][0][0] , dp[1][0][1]));

    return 0;
}

Compilation message (stderr)

xanadu.cpp: In function 'void dfs(int, int)':
xanadu.cpp:10:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   10 |     for (i = 0 ; i < v[nod].size() ; i++){
      |                  ~~^~~~~~~~~~~~~~~
xanadu.cpp:31:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   31 |     for (i = 0 ; i < v[nod].size() ; i++){
      |                  ~~^~~~~~~~~~~~~~~
xanadu.cpp:56:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   56 |     for (i = 0 ; i < v[nod].size() ; i++){
      |                  ~~^~~~~~~~~~~~~~~
xanadu.cpp: In function 'int main()':
xanadu.cpp:87:12: warning: ignoring return value of 'int fscanf(FILE*, const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   87 |     fscanf (fin,"%d",&n);
      |     ~~~~~~~^~~~~~~~~~~~~
xanadu.cpp:89:16: warning: ignoring return value of 'int fscanf(FILE*, const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   89 |         fscanf (fin,"%d%d",&x,&y);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~
xanadu.cpp:94:16: warning: ignoring return value of 'int fscanf(FILE*, const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   94 |         fscanf (fin,"%d",&c[i]);
      |         ~~~~~~~^~~~~~~~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 15 / 15
• Subtask 3: 10 / 10
• Subtask 4: 40 / 40
• Subtask 5: 30 / 30