Submission #823915

#	Time	Username	Problem	Language	Result	Execution time	Memory
823915		tset	The Xana coup (BOI21_xanadu)	C++14	50 / 100	77 ms	26116 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;
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] != INF)
    {
        return dp[isParentT][isMeT][nde];
    }
    int nbFils = filsDe[nde].size();
    int totT = isParentT + isMeT + initState[nde];
    int ans = INF;
    if(totT %2 == 0)
    {//We need to toggle 0 or two child(ren).
        if(nbFils == 0)
        {
            ans = 0;
        }
        if(nbFils == 1)
        {
            ans = fDP(isMeT, 0, filsDe[nde][0]);
        }
        if(nbFils == 2)
        {
            ans = min(fDP(isMeT, 0, filsDe[nde][0]) + fDP(isMeT, 0, filsDe[nde][1]),
                      fDP(isMeT, 1, filsDe[nde][0]) + fDP(isMeT, 1, filsDe[nde][1]) + 2);
        }
    }
    else
    {
        //We need to toggle only one child.
        if(nbFils == 0)
        {
            ans = INF;
        }
        if(nbFils == 1)
        {
            ans = fDP(isMeT, 1, filsDe[nde][0]) + 1;
        }
        if(nbFils == 2)
        {
            ans = min(fDP(isMeT, 0, filsDe[nde][0]) + fDP(isMeT, 1, filsDe[nde][1]) + 1,
                      fDP(isMeT, 1, filsDe[nde][0]) + fDP(isMeT, 0, filsDe[nde][1]) + 1);
        }
    }
    dp[isParentT][isMeT][nde] = ans;
    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;
    for(int iNde = 1; iNde <= N; iNde ++)
    {
        if(nxt[iNde].size() < 3)
        {
            root = iNde;
            break;
        }
    }
    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, INF)));
    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:74:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   74 |     scanf("%lld", &N);
      |     ~~~~~^~~~~~~~~~~~
xanadu.cpp:82:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   82 |         scanf("%lld%lld", &u, &v);
      |         ~~~~~^~~~~~~~~~~~~~~~~~~~
xanadu.cpp:100:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  100 |         scanf("%lld", &initState[iNde]);
      |         ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 5
• Subtask 2: 0 / 15
• Subtask 3: 10 / 10
• Subtask 4: 40 / 40
• Subtask 5: 0 / 30