結果
問題 | No.1227 I hate ThREE |
ユーザー |
|
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 |
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ファイルパターン | 結果 |
---|---|
sample | AC * 3 |
other | AC * 33 |
ソースコード
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();}}}