結果

問題 No.1227 I hate ThREE
ユーザー 37zigen37zigen
提出日時 2020-07-28 21:12:36
言語 Java
(openjdk 23)
結果
AC  
実行時間 679 ms / 2,000 ms
コード長 3,734 bytes
コンパイル時間 2,493 ms
コンパイル使用メモリ 82,504 KB
実行使用メモリ 268,148 KB
最終ジャッジ日時 2025-01-02 05:17:00
合計ジャッジ時間 20,362 ms
ジャッジサーバーID
(参考情報)
judge5 / judge3
このコードへのチャレンジ
(要ログイン)
ファイルパターン 結果
sample AC * 3
other AC * 33
権限があれば一括ダウンロードができます

ソースコード

diff #
プレゼンテーションモードにする

import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.NoSuchElementException;
public class Main {
public static void main(String[] args) {
new Main().run();
}
long pow(long a,long n) {
long ret=1;
for (;n>0;n>>=1,a=a*a%MOD) if (n%2==1) ret=ret*a%MOD;
return ret;
}
void dfs(int cur,int par,ArrayList<Integer>[] g,int C) {
for (int curc=1;curc<dp[cur].length;++curc) {
dp[cur][curc]=1;
}
for (int dst:g[cur]) {
if (dst==par) continue;
dfs(dst,cur,g,C);
for (int curc=1;curc<dp[cur].length;++curc) {
long sum=0;
for (int d=-3;d<=3;d+=6) {
int nextc=curc+d;
if (nextc<1||nextc>C||nextc>=dp[dst].length) continue;
sum+=dp[dst][nextc];
sum%=MOD;
}
dp[cur][curc]*=sum;
dp[cur][curc]%=MOD;
}
}
}
final long MOD=(long)1e9+7;
int MAXN=3000;
long[][] dp=new long[MAXN][3*MAXN+1];
void run() {
FastScanner sc=new FastScanner();
int N=sc.nextInt();
int C=sc.nextInt();
int[] a=new int[N-1];
int[] b=new int[N-1];
ArrayList<Integer>[] g=new ArrayList[N];
for (int i=0;i<N;++i) g[i]=new ArrayList<>();
for (int i=0;i<N-1;++i) {
a[i]=sc.nextInt()-1;
b[i]=sc.nextInt()-1;
g[a[i]].add(b[i]);
g[b[i]].add(a[i]);
}
if (C<=6000) {
dfs(0,-1,g,C);
long ans=0;
for (int c=1;c<=C;++c) {
ans=(ans+dp[0][c])%MOD;
}
System.out.println(ans);
} else {
dfs(0,-1,g,C);
long s=0;
for (int c=1;c<=3000;++c) {
s=(s+dp[0][c])%MOD;
}
long ans=2*s+(C-6000)%MOD*pow(2,N-1)%MOD;
ans=(ans%MOD+MOD)%MOD;
System.out.println(ans);
}
}
void tr(Object...objects) {System.out.println(Arrays.deepToString(objects));}
class FastScanner {
private final InputStream in = System.in;
private final byte[] buffer = new byte[1024];
private int ptr = 0;
private int buflen = 0;
private boolean hasNextByte() {
if (ptr < buflen) {
return true;
}else{
ptr = 0;
try {
buflen = in.read(buffer);
} catch (IOException e) {
e.printStackTrace();
}
if (buflen <= 0) {
return false;
}
}
return true;
}
private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1;}
private boolean isPrintableChar(int c) { return 33 <= c && c <= 126;}
private void skipUnprintable() { while(hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++;}
public boolean hasNext() { skipUnprintable(); return hasNextByte();}
public String next() {
if (!hasNext()) throw new NoSuchElementException();
StringBuilder sb = new StringBuilder();
int b = readByte();
while(isPrintableChar(b)) {
sb.appendCodePoint(b);
b = readByte();
}
return sb.toString();
}
public long nextLong() {
if (!hasNext()) throw new NoSuchElementException();
long n = 0;
boolean minus = false;
int b = readByte();
if (b == '-') {
minus = true;
b = readByte();
}
if (b < '0' || '9' < b) {
throw new NumberFormatException();
}
while(true){
if ('0' <= b && b <= '9') {
n *= 10;
n += b - '0';
}else if(b == -1 || !isPrintableChar(b)){
return minus ? -n : n;
}else{
throw new NumberFormatException();
}
b = readByte();
}
}
public int nextInt() {
return (int)nextLong();
}
}
}
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