Submission #824000

#	Time	Username	Problem	Language	Result	Execution time	Memory
824000		tset	The Xana coup (BOI21_xanadu)	C++14	100 / 100	102 ms	40756 KiB

xanadu

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

const int INF = 1e9 + 42;

vector<vector<int> > nxt;
vector<vector<int>> filsDe;
vector<int> pereDe;
vector<vector<vector<int > > > dp;
vector<int > initState;
int occ = 0;

void dfsInit(int nde,int prc )
{   
    pereDe[nde] = prc;
    for(int iV: nxt[nde])
    {
        if(iV != prc)
        {
            filsDe[nde].push_back(iV);
            dfsInit(iV, nde);
        }
    }
}

int fDP(int isParentT, int isMeT, int nde)
{
    if(dp[isParentT][isMeT][nde] != -1)
    {
        return dp[isParentT][isMeT][nde];
    }
    int nbFils = filsDe[nde].size();
    int totT = isParentT + isMeT + initState[nde];
    int ans = INF;
    int sumNoToggle = 0;
    vector<int > diff(nbFils);
    vector<int > diffCumul(nbFils+1);
    for(int iF = 0; iF < nbFils; iF++)
    {
        int costToggled = fDP(isMeT, 1, filsDe[nde][iF]) + 1;
        int costNoToggled = fDP(isMeT, 0, filsDe[nde][iF]);
        sumNoToggle += costNoToggled;
        diff[iF] = costToggled - costNoToggled;
    }
    sort(diff.begin(), diff.end());
    diffCumul[0] = 0;
    for(int i=1; i<= nbFils; i++)
    {
        diffCumul[i] = diffCumul[i-1]+ diff[i-1];
    }

    if(totT %2 == 0)
    {//We need to toggle an even nb of children.
        for(int i = 0; i<= nbFils; i+=2)
        {
            ans = min(ans,  sumNoToggle + diffCumul[i]);
        }
    }
    else
    {
        //We need to toggle an odd nb of children.
        for(int i = 1; i<= nbFils; i+=2)
        {
            ans = min(ans, sumNoToggle + diffCumul[i]);
        }
    }
    if(ans >= INF)
        ans = INF;
    dp[isParentT][isMeT][nde] = ans;
    //printf("%lld\n", occ++);

    return dp[isParentT][isMeT][nde];

}

signed main()
{
    int N;
    scanf("%lld", &N);
    int nbArretes = N-1;
    nxt.resize(N+1);
    filsDe.resize(N+1);
    pereDe.resize(N+1);
    for(int iA = 0; iA < nbArretes; iA++)
    {
        int u, v;
        scanf("%lld%lld", &u, &v);
        nxt[u].push_back(v);
        nxt[v].push_back(u);
    }
    int root = 1;

    dfsInit(root, root);
    initState.resize(N+1);
    for(int iNde = 1; iNde <=N; iNde++)
    {
        scanf("%lld", &initState[iNde]);
    }
    dp.resize(2, vector<vector<int>>(2, vector<int>(N+1, -1)));
    int ans = fDP(0, 0, root);
    ans = min(ans, fDP(0, 1, root) + 1);
    if(ans >= INF)
        printf("impossible\n");
    else 
        printf("%lld", ans);
}

Compilation message (stderr)

xanadu.cpp: In function 'int main()':
xanadu.cpp:80:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   80 |     scanf("%lld", &N);
      |     ~~~~~^~~~~~~~~~~~
xanadu.cpp:88:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   88 |         scanf("%lld%lld", &u, &v);
      |         ~~~~~^~~~~~~~~~~~~~~~~~~~
xanadu.cpp:98:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   98 |         scanf("%lld", &initState[iNde]);
      |         ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~

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