/* https://hsin.hr/ceoi/competition/ceoi2021_day2_editorial.pdf */
#include <stdio.h>
#include <stdlib.h>
#define N 10000
#define MD 1000000007
#define INF 0x3f3f3f3f
int min(int a, int b) { return a < b ? a : b; }
int max(int a, int b) { return a > b ? a : b; }
int pp2[N + 1];
void init() {
int i;
pp2[0] = 1;
for (i = 1; i <= N; i++)
pp2[i] = pp2[i - 1] * 2 % MD;
}
int mem[(N - 1) * 2], *ptr = mem;
int *ej[N], eo[N], pp[N], n, k; char type[N];
int i_, l;
int ii[N]; char path[N];
void dfs1(int p, int i, int d) {
int o;
pp[i] = p;
d++;
if (l < d)
l = d, i_ = i;
for (o = eo[i]; o--; ) {
int j = ej[i][o];
if (j != p)
dfs1(i, j, d);
}
}
int gg[N], dd[N], hh[N];
void dfs2(int p, int i, int g, int d) {
int o;
gg[i] = g, dd[i] = d, hh[i] = 0;
for (o = eo[i]; o--; ) {
int j = ej[i][o];
if (j != p && !path[j]) {
dfs2(i, j, g, d + 1);
hh[i] = max(hh[i], hh[j] + 1);
}
}
}
int dfs3(int p, int i, int d) {
int o, x;
if (d == 0 || type[i] == -1)
return 1;
x = 1;
for (o = eo[i]; o--; ) {
int j = ej[i][o];
if (j != p)
x = (long long) x * dfs3(i, j, d - 1) % MD;
}
return (x + 1) % MD;
}
int cc[N], dp[N], dq[N], dr[N];
int dfs4(int p, int i) {
int o, p1, p2;
dp[i] = -INF, dq[i] = 0, dr[i] = -1, p1 = p2 = -INF;
for (o = eo[i]; o--; ) {
int j = ej[i][o];
if (j != p && !path[j] && type[j] == 1) {
if (!dfs4(i, j))
return 0;
dp[i] = max(dp[i], dp[j]);
if (p1 < dp[j])
p2 = p1, p1 = dp[j];
else if (p2 < dp[j])
p2 = dp[j];
if (cc[i] == 0 && dq[i] + dq[j] + 1 >= k - 1)
return 0;
dq[i] = max(dq[i], dq[j] + 1);
if (dr[j] != -1)
dr[i] = dr[j] + 1;
}
}
if (cc[i] == 1)
dp[i] = hh[i], dq[i] = -1, dr[i] = 0;
else if (p2 != -INF && dr[i] * 2 <= k - 1 && dr[i] * 2 + p1 + p2 >= k - 1)
return 0;
return 1;
}
char bad[N];
void mark_bad() {
static int aa[N + 1];
int g, r, i, d;
for (g = 0; g < l; g++)
if (type[ii[g]] == 1) {
int lower, upper;
lower = g + 1, upper = min(g * 2, k - 1);
if (lower <= upper)
aa[lower]++, aa[upper + 1]--;
lower = max(g * 2 - l + 1, l - k), upper = g - 1;
if (lower <= upper) {
lower %= k, upper %= k;
aa[lower]++, aa[upper + 1]--;
if (lower > upper)
aa[0]++;
}
}
for (r = 1; r < k; r++)
aa[r] += aa[r - 1];
for (r = 0; r < k; r++)
if (aa[r])
bad[r] = 1;
for (i = 0; i < n; i++)
if (!path[i] && type[i] == 1) {
int r1, r2;
g = gg[i], d = dd[i];
r1 = (g + d) % k;
r2 = (g - d % k + k) % k;
if (r1 != r2) {
if (g >= r1 && g <= (l - 1 - r1) / k * k + r1)
bad[r1] = 1;
if (g >= r2 && g <= (l - 1 - r2) / k * k + r2)
bad[r2] = 1;
}
}
}
int yes, ans;
void try(int r) {
int g, gl, gr, i, d, x;
if (bad[r])
return;
gl = r, gr = (l - 1 - r) / k * k + r;
for (i = 0; i < n; i++) {
g = gg[i], d = dd[i];
if (!path[i] && type[i] == 1)
cc[i] = g >= gl ? ((g + d) % k == r ? 1 : 0) : ((g - d % k + k) % k == r ? 1 : 0);
}
x = 1;
for (i = 0; i < n; i++)
if (!path[i] && type[i] == 0 && (path[pp[i]] || type[pp[i]] == 1)) {
g = gg[i], d = dd[i];
if (g + dd[i] + hh[i] >= k - 1) {
if (g < gl)
x = (long long) x * dfs3(pp[i], i, k - 1 - (g + dd[i])) % MD;
} else {
if (g > gr)
x = (long long) x * dfs3(pp[i], i, k - 1 - (l - 1 - g + dd[i])) % MD;
}
}
for (g = 0; g < l; g++)
if (type[ii[g]] == 1 && !dfs4(-1, ii[g]))
return;
yes = 1, ans = (ans + x) % MD;
}
int main() {
static int uu[N - 1], vv[N - 1];
int g, h, i, j, u, v, d, r;
init();
scanf("%d%d", &n, &k);
if (k == 2) {
printf("YES\n");
printf("2\n");
return 0;
}
for (h = 0; h < n - 1; h++) {
scanf("%d%d", &i, &j), i--, j--;
uu[h] = i, vv[h] = j;
eo[i]++, eo[j]++;
}
for (i = 0; i < n; i++) {
ej[i] = ptr, ptr += eo[i];
eo[i] = 0;
}
for (h = 0; h < n - 1; h++) {
i = uu[h], j = vv[h];
ej[i][eo[i]++] = j, ej[j][eo[j]++] = i;
}
i_ = -1, l = -1, dfs1(-1, 0, 0), u = i_;
i_ = -1, l = -1, dfs1(-1, u, 0), v = i_;
if (l < k) {
printf("YES\n");
printf("%d\n", pp2[n]);
return 0;
}
for (i = v, d = l - 1; i != u; i = pp[i], d--)
path[ii[d] = i] = 1;
path[ii[0] = u] = 1;
for (g = 0; g < l; g++)
dfs2(-1, ii[g], g, 0);
for (i = 0; i < n; i++) {
g = gg[i];
if (max(g, l - 1 - g) + dd[i] + hh[i] < k - 1)
type[i] = -1;
else if (min(g, l - 1 - g) + dd[i] + hh[i] >= k - 1)
type[i] = 1;
else
type[i] = 0;
}
mark_bad();
yes = 0, ans = 0;
for (r = 0; r < k; r++)
try(r);
if (yes) {
printf("YES\n");
for (i = 0; i < n; i++)
if (!path[i] && type[i] == -1)
ans = ans * 2 % MD;
printf("%d\n", ans);
} else {
printf("NO\n");
printf("0\n");
}
return 0;
}
Compilation message
wells.c: In function 'main':
wells.c:183:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
183 | scanf("%d%d", &n, &k);
| ^~~~~~~~~~~~~~~~~~~~~
wells.c:190:3: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
190 | scanf("%d%d", &i, &j), i--, j--;
| ^~~~~~~~~~~~~~~~~~~~~
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
0 ms |
332 KB |
Output is correct |
| 2 |
Correct |
0 ms |
332 KB |
Output is correct |
| 3 |
Correct |
0 ms |
332 KB |
Output is correct |
| 4 |
Correct |
0 ms |
332 KB |
Output is correct |
| 5 |
Correct |
0 ms |
332 KB |
Output is correct |
| 6 |
Correct |
1 ms |
332 KB |
Output is correct |
| 7 |
Correct |
0 ms |
332 KB |
Output is correct |
| 8 |
Incorrect |
0 ms |
332 KB |
Output isn't correct |
| 9 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
0 ms |
332 KB |
Output is correct |
| 2 |
Correct |
0 ms |
332 KB |
Output is correct |
| 3 |
Correct |
0 ms |
332 KB |
Output is correct |
| 4 |
Correct |
0 ms |
332 KB |
Output is correct |
| 5 |
Correct |
0 ms |
332 KB |
Output is correct |
| 6 |
Correct |
1 ms |
332 KB |
Output is correct |
| 7 |
Correct |
0 ms |
332 KB |
Output is correct |
| 8 |
Incorrect |
0 ms |
332 KB |
Output isn't correct |
| 9 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
0 ms |
332 KB |
Output is correct |
| 2 |
Correct |
0 ms |
332 KB |
Output is correct |
| 3 |
Correct |
0 ms |
332 KB |
Output is correct |
| 4 |
Correct |
0 ms |
332 KB |
Output is correct |
| 5 |
Correct |
0 ms |
332 KB |
Output is correct |
| 6 |
Correct |
1 ms |
332 KB |
Output is correct |
| 7 |
Correct |
0 ms |
332 KB |
Output is correct |
| 8 |
Incorrect |
0 ms |
332 KB |
Output isn't correct |
| 9 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
0 ms |
332 KB |
Output is correct |
| 2 |
Correct |
0 ms |
332 KB |
Output is correct |
| 3 |
Correct |
0 ms |
332 KB |
Output is correct |
| 4 |
Correct |
0 ms |
332 KB |
Output is correct |
| 5 |
Correct |
0 ms |
332 KB |
Output is correct |
| 6 |
Correct |
1 ms |
332 KB |
Output is correct |
| 7 |
Correct |
0 ms |
332 KB |
Output is correct |
| 8 |
Incorrect |
0 ms |
332 KB |
Output isn't correct |
| 9 |
Halted |
0 ms |
0 KB |
- |
