| # |
Submission time |
Handle |
Problem |
Language |
Result |
Execution time |
Memory |
| 585628 |
2022-06-29T06:44:34 Z |
박상훈(#8384) |
Star Trek (CEOI20_startrek) |
C++17 |
|
2 ms |
2644 KB |
#include <bits/stdc++.h>
typedef long long ll;
using namespace std;
const int MOD = 1e9+7;
vector<int> adj[100100];
bool _win[100100], _win_pa[100100], _win_root[100100], ok[100100];
ll S[100100];
void dfs1(int s, int pa = -1){
int wcnt = 0, lcnt = 0;
for (auto &v:adj[s]) if (v!=pa){
dfs1(v, s);
if (_win[v]) wcnt++;
else lcnt++;
}
if (!lcnt) _win[s] = 0;
else _win[s] = 1;
if (lcnt<=1) ok[s] = 1;
}
void dfs2(int s, int pa = -1){
int wcnt = 0, lcnt = 0;
for (auto &v:adj[s]) if (v!=pa){
if (_win[v]) wcnt++;
else lcnt++;
}
if (pa!=-1){
if (_win_pa[s]) wcnt++;
else lcnt++;
}
for (auto &v:adj[s]) if (v!=pa){
if (_win[v]) wcnt--;
else lcnt--;
if (!lcnt) _win_pa[v] = 0;
else _win_pa[v] = 1;
if (_win[v]) wcnt++;
else lcnt++;
}
if (!lcnt) _win_root[s] = 0;
else _win_root[s] = 1;
for (auto &v:adj[s]) if (v!=pa) dfs2(v, s);
}
int lscnt[100100], lscnt_pa[100100], lscnt_root[100100];
void dfs3(int s, int pa = -1){
if (!_win[s]) lscnt[s]++;
int lcnt = 0, wcnt = 0;
for (auto &v:adj[s]) if (v!=pa){
dfs3(v, s);
if (!_win[v]) lcnt++;
else wcnt++;
}
for (auto &v:adj[s]) if (v!=pa){
if (lcnt==1 && !_win[v]) lscnt[s] += lscnt[v];
else if (lcnt==0) lscnt[s] += lscnt[v];
}
}
void dfs4(int s, int pa = -1){
///count
int wcnt = 0, lcnt = 0, sum = 0;
vector<int> L;
for (auto &v:adj[s]) if (v!=pa){
if (_win[v]) wcnt++;
else lcnt++;
sum += lscnt[v];
if (!_win[v]) L.push_back(v);
}
if (pa!=-1){
if (_win_pa[s]) wcnt++;
else lcnt++;
sum += lscnt_pa[s];
}
///calc pa
for (auto &v:adj[s]) if (v!=pa){
if (_win[v]) wcnt--;
else lcnt--;
sum -= lscnt[v];
if (!lcnt) lscnt_pa[v] = sum+1;
else if (lcnt==1){
if (pa!=-1 && !_win_pa[s]) lscnt_pa[v] = lscnt_pa[s];
else{
if (L[0]!=v) lscnt_pa[v] = lscnt[L[0]];
else lscnt_pa[v] = lscnt[L[1]];
}
}
if (_win[v]) wcnt++;
else lcnt++;
sum += lscnt[v];
}
///calc root
if (!lcnt) lscnt_root[s] = sum+1;
else if (lcnt==1){
if (pa!=-1 && !_win_pa[s]) lscnt_root[s] = lscnt_pa[s];
else lscnt_root[s] = lscnt[L[0]];
}
for (auto &v:adj[s]) if (v!=pa) dfs4(v, s);
}
ll pw(ll a, ll e){
if (!e) return 1;
ll ret = pw(a, e/2);
if (e&1) return ret*ret%MOD*a%MOD;
return ret*ret%MOD;
}
int main(){
int n;
ll d;
scanf("%d %lld", &n, &d);
if (n==2) {printf("%lld\n", pw(4, d)); return 0;}
for (int i=1;i<=n-1;i++){
int x, y;
scanf("%d %d", &x, &y);
adj[x].push_back(y);
adj[y].push_back(x);
}
dfs1(1);
dfs2(1);
dfs3(1);
dfs4(1);
/*
for (int i=1;i<=n;i++) printf("%d ", _win[i]); printf("\n");
for (int i=1;i<=n;i++) printf("%d ", _win_pa[i]); printf("\n");
for (int i=1;i<=n;i++) printf("%d ", _win_root[i]); printf("\n");
for (int i=1;i<=n;i++) printf("%d ", ok[i]); printf("\n");
*/
ll ans = 0, T = 0, L = 0;
for (int i=1;i<=n;i++){
if (_win[i]) T += lscnt_root[i];
else T -= lscnt_root[i], L++;
if (T>=MOD) T -= MOD;
if (T<0) T += MOD;
}
S[0] = L;
for (int i=1;i<=d;i++){
S[i] = (pw(n, (i-1)*2) * L % MOD + T * S[i-1] % MOD) % MOD;
}
if (_win[1]) ans = (pw(n, d*2) + MOD) - (lscnt_root[1] * S[d-1] % MOD);
else ans = lscnt_root[1] * S[d-1] % MOD;
ans %= MOD;
printf("%lld\n", ans);
return 0;
}
/*
int lcnt = 0;
for (int i=1;i<=n;i++) if (!_win_root[i]) lcnt++;
ll ans = 0;
if (_win[1]) ans = (ll)n*n - (ll)lscnt[1] * lcnt;
else ans = (ll)lscnt[1] * lcnt;
ans %= MOD;
printf("%lld\n", ans);
*/
Compilation message
startrek.cpp: In function 'int main()':
startrek.cpp:126:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
126 | scanf("%d %lld", &n, &d);
| ~~~~~^~~~~~~~~~~~~~~~~~~
startrek.cpp:131:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
131 | scanf("%d %d", &x, &y);
| ~~~~~^~~~~~~~~~~~~~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
2644 KB |
Output is correct |
| 2 |
Incorrect |
2 ms |
2644 KB |
Output isn't correct |
| 3 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
2644 KB |
Output is correct |
| 2 |
Correct |
1 ms |
2644 KB |
Output is correct |
| 3 |
Correct |
2 ms |
2644 KB |
Output is correct |
| 4 |
Correct |
2 ms |
2644 KB |
Output is correct |
| 5 |
Correct |
2 ms |
2644 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
2 ms |
2644 KB |
Output is correct |
| 2 |
Incorrect |
1 ms |
2644 KB |
Output isn't correct |
| 3 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
2 ms |
2644 KB |
Output is correct |
| 2 |
Incorrect |
1 ms |
2644 KB |
Output isn't correct |
| 3 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
2 ms |
2644 KB |
Output is correct |
| 2 |
Incorrect |
1 ms |
2644 KB |
Output isn't correct |
| 3 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
2 ms |
2644 KB |
Output is correct |
| 2 |
Incorrect |
1 ms |
2644 KB |
Output isn't correct |
| 3 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
2 ms |
2644 KB |
Output is correct |
| 2 |
Incorrect |
1 ms |
2644 KB |
Output isn't correct |
| 3 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
2644 KB |
Output is correct |
| 2 |
Incorrect |
2 ms |
2644 KB |
Output isn't correct |
| 3 |
Halted |
0 ms |
0 KB |
- |
