結果
問題 |
No.1011 Infinite Stairs
|
ユーザー |
|
提出日時 | 2020-03-20 22:15:59 |
言語 | Java (openjdk 23) |
結果 |
AC
|
実行時間 | 113 ms / 2,000 ms |
コード長 | 2,826 bytes |
コンパイル時間 | 2,466 ms |
コンパイル使用メモリ | 77,908 KB |
実行使用メモリ | 60,232 KB |
最終ジャッジ日時 | 2024-07-17 11:51:26 |
合計ジャッジ時間 | 6,406 ms |
ジャッジサーバーID (参考情報) |
judge5 / judge1 |
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ファイルパターン | 結果 |
---|---|
sample | AC * 3 |
other | AC * 24 |
ソースコード
import java.io.FileNotFoundException; import java.io.IOException; import java.io.InputStream; import java.util.Arrays; import java.util.NoSuchElementException; public class Main { public static void main(String[] args) throws FileNotFoundException { long t = System.currentTimeMillis(); new Main().run(); System.err.println(System.currentTimeMillis() - t); } Scanner sc = new Scanner(); final long MOD=(long)1e9+7; long[] fac=new long[500000]; long[] ifac=new long[500000]; long[] inv=new long[500000]; { fac[0]=fac[1]=ifac[0]=ifac[1]=inv[0]=inv[1]=1; for(int i=2;i<fac.length;++i) { fac[i]=i*fac[i-1]%MOD; inv[i]=MOD-inv[(int)(MOD%i)]*(MOD/i)%MOD; ifac[i]=inv[i]*ifac[i-1]%MOD; } } long comb(int n,int k) { if(k<0||n-k<0)return 0; return fac[n]*ifac[k]%MOD*ifac[n-k]%MOD; } void run() { int N=sc.nextInt(); int d=sc.nextInt(); int K=sc.nextInt(); long ans=0; for(int i=0;i<=N;++i) { ans+=comb(N,i)*(i%2==0?1:-1)*comb(N+(K-N-d*i)-1,K-N-d*i)%MOD; ans%=MOD; } System.out.println((ans+MOD)%MOD); } class Scanner { 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(); } } static void tr(Object... objects) { System.out.println(Arrays.deepToString(objects)); } }