Submission #567127

#	Time	Username	Problem	Language	Result	Execution time	Memory
567127		azberjibiou	Star Trek (CEOI20_startrek)	C++17	100 / 100	94 ms	15868 KiB

startrek

#include <bits/stdc++.h>
#define gibon ios::sync_with_stdio(false); cin.tie(0);
#define fir first
#define sec second
#define pdd pair<long double, long double>
#define pii pair<int, int>
#define pll pair<ll, ll>
#define ld long double
#define pmax pair<__int128, __int128>
#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
typedef long long ll;
using namespace std;
int dx[4]= {0, 1, 0, -1}, dy[4]= {1, 0, -1, 0};
int ddx[8]={1, 1, 0, -1, -1, -1, 0, 1}, ddy[8]={0, 1, 1, 1, 0, -1, -1, -1};
const int mxN=100025;
const int mxM=300005;
const int mxK=1000000000;
const ll MOD=1000'000'007;
const ll INF=1000000000000000005;
ll N, D;
vector <int> v[mxN];
int outw[mxN];
int downw[mxN], upw[mxN];
bool W[mxN];
ll degL[mxN];
ll leafw2[mxN], sizl2[mxN], par2[mxN];
ll numw;
int match[mxN];
ll swapL1[mxN];
void dfs_downw(int now, int pre)
{
    for(int nxt : v[now])   if(nxt!=pre)
    {
        dfs_downw(nxt, now);
    }
    downw[now]=(outw[now]==0 ? 1 : 0);
    if(now!=1)  outw[pre]+=downw[now];
}
void dfs_upw(int now, int pre)
{
    if(now!=1)
    {
        upw[now]=(outw[pre]-downw[now]==0 ? 1 : 0);
        outw[now]+=upw[now];
    }
    for(int nxt : v[now])   if(nxt!=pre)
    {
        dfs_upw(nxt, now);
    }
}
int findpar(int a)
{
    return (par2[a]==a ? a : par2[a]=findpar(par2[a]));
}
void onion(int a, int b)
{
    int p=findpar(a), q=findpar(b);
    par2[p]=q;  sizl2[q]+=sizl2[p]; leafw2[q]+=leafw2[p];
}
int dfs_match(int now, int pre)
{
    for(int nxt : v[now])   if(nxt!=pre && W[nxt] && degL[nxt]==0)
    {
        int tmp=dfs_match(nxt, now);
        if(tmp!=0)  match[now]=tmp, match[tmp]=now;
    }
    if(match[now])  return 0;
    else    return now;
}
int dfs_swap(int now)
{
    if(swapL1[now]!=0)  return swapL1[now];
    ll sum=1;
    for(int nxt : v[match[now]])    if(nxt!=now && W[nxt] && degL[nxt]==0)
    {
        sum+=dfs_swap(nxt);
    }
    return swapL1[now]=sum;
}
ll f(ll a)
{
    return (a%MOD+MOD)%MOD;
}
ll mypow(ll a, ll b)
{
    if(b==0)    return 1;
    if(b==1)    return f(a);
    ll tmp=mypow(a, b/2);
    tmp*=tmp;   tmp%=MOD;
    if(b%2) tmp*=a; tmp%=MOD;
    return tmp;
}
int main()
{
    gibon
    cin >> N >> D;
    for(int i=1;i<N;i++)
    {
        int a, b;   cin >> a >> b;
        v[a].push_back(b);
        v[b].push_back(a);
    }
    dfs_downw(1, -1);
    dfs_upw(1, -1);
    for(int i=1;i<=N;i++)
    {
        W[i]=(outw[i]>=1);
        numw+=W[i];
    }
    for(int i=1;i<=N;i++)   for(int ele : v[i]) if(!W[ele]) degL[i]++;
    for(int i=1;i<=N;i++)
    {
        par2[i]=i;
        if(degL[i]==1) leafw2[i]=1;
        if(!W[i])   sizl2[i]=1;
    }
    for(int i=1;i<=N;i++)   for(int ele : v[i]) if(degL[ele]<3 && !W[i]) onion(i, ele);
    for(int i=1;i<=N;i++)   if(W[i] && degL[i]==0 && match[i]==0)   dfs_match(i, -1);
    for(int i=1;i<=N;i++)   if(W[i] && degL[i]==0)  dfs_swap(i);
    ll k1=numw, k2=0;
    for(int i=1;i<=N;i++)   k2-=swapL1[i];  k2=f(k2);
    for(int i=1;i<=N;i++)   if(findpar(i)==i)   k2+=sizl2[i]*(sizl2[i]-leafw2[i]), k2=f(k2);
    ll recur;
    if(D==1)    recur=numw;
    else if(k2==0)  recur=mypow(N, 2*(D-1));
    else    recur=f(f(f(f(f(N*N)*k1)+f(N*k2))*f(mypow(N, 2*(D-1))-mypow(MOD-k2, D-1)))*mypow(f(N*N+k2), MOD-2))+f(f((D%2 ? 1 : MOD-1)*numw)*mypow(k2, D-1));
    recur=f(recur);
    ll powN=mypow(N, 2*D-1);
    if(W[1])
    {
        ll ans=powN*N%MOD;
        if(degL[1]==0)  ans-=(powN-recur)*swapL1[1]; ans=f(ans);
        if(degL[1]==1)  ans-=(powN-recur)*sizl2[findpar(1)]; ans=f(ans);
        cout << ans;
    }
    else
    {
        ll ans=0;
        ans+=(powN-recur)*sizl2[findpar(1)];
        cout << f(ans);
    }
}

Compilation message (stderr)

startrek.cpp: In function 'll mypow(ll, ll)':
startrek.cpp:92:5: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
   92 |     if(b%2) tmp*=a; tmp%=MOD;
      |     ^~
startrek.cpp:92:21: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'if'
   92 |     if(b%2) tmp*=a; tmp%=MOD;
      |                     ^~~
startrek.cpp: In function 'int main()':
startrek.cpp:123:5: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
  123 |     for(int i=1;i<=N;i++)   k2-=swapL1[i];  k2=f(k2);
      |     ^~~
startrek.cpp:123:45: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'for'
  123 |     for(int i=1;i<=N;i++)   k2-=swapL1[i];  k2=f(k2);
      |                                             ^~
startrek.cpp:134:9: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
  134 |         if(degL[1]==0)  ans-=(powN-recur)*swapL1[1]; ans=f(ans);
      |         ^~
startrek.cpp:134:54: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'if'
  134 |         if(degL[1]==0)  ans-=(powN-recur)*swapL1[1]; ans=f(ans);
      |                                                      ^~~
startrek.cpp:135:9: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
  135 |         if(degL[1]==1)  ans-=(powN-recur)*sizl2[findpar(1)]; ans=f(ans);
      |         ^~
startrek.cpp:135:62: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'if'
  135 |         if(degL[1]==1)  ans-=(powN-recur)*sizl2[findpar(1)]; ans=f(ans);
      |                                                              ^~~

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