Codeforces Round #359 Div2 C. Robbers' watch
解法
よく考えると状態はくらいしかない。
コード
import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.io.PrintWriter; import java.util.Arrays; import java.util.NoSuchElementException; public class C { private static class Task { int getDigitLength(int h) { if (h == 1) return 1; h--; int cnt = 0; while (h > 0) { h /= 7; cnt++; } return cnt; } String base7(int h) { String s = ""; while (h > 0) { s = String.valueOf(h % 7) + s; h /= 7; } return s; } void solve(FastScanner in, PrintWriter out) { int N = in.nextInt(); int M = in.nextInt(); int dN = getDigitLength(N); int dM = getDigitLength(M); if (dN + dM > 7) { out.println(0); return; } int suffixRoom = 1; while (suffixRoom <= M) suffixRoom *= 7; int ans = 0; boolean[] check = new boolean[7]; loop: for (int i = 0; i < 5764802; i++) { Arrays.fill(check, false); int prefix = i / suffixRoom; int suffix = i % suffixRoom; if (prefix >= N || suffix >= M) continue; for (int j = 0; j < dN; j++) { int k = prefix % 7; if (check[k]) { continue loop; } check[k] = true; prefix /= 7; } for (int j = 0; j < dM; j++) { int k = suffix % 7; if (check[k]) { continue loop; } check[k] = true; suffix /= 7; } // out.println(base7(i / suffixRoom) + " " + base7(i % suffixRoom)); ans++; } out.println(ans); } } // Template public static void main(String[] args) { OutputStream outputStream = System.out; FastScanner in = new FastScanner(); PrintWriter out = new PrintWriter(outputStream); Task solver = new Task(); solver.solve(in, out); out.close(); } private static class FastScanner { private final InputStream in = System.in; private final byte[] buffer = new byte[1024]; private int ptr = 0; private int bufferLength = 0; private boolean hasNextByte() { if (ptr < bufferLength) { return true; } else { ptr = 0; try { bufferLength = in.read(buffer); } catch (IOException e) { e.printStackTrace(); } if (bufferLength <= 0) { return false; } } return true; } private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1; } private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126; } private void skipUnprintable() { while (hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++; } 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(); } 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(); } } double nextDouble() { return Double.parseDouble(next()); } double[] nextDoubleArray(int n) { double[] array = new double[n]; for (int i = 0; i < n; i++) { array[i] = nextDouble(); } return array; } double[][] nextDoubleMap(int n, int m) { double[][] map = new double[n][]; for (int i = 0; i < n; i++) { map[i] = nextDoubleArray(m); } return map; } public int nextInt() { return (int) nextLong(); } public int[] nextIntArray(int n) { int[] array = new int[n]; for (int i = 0; i < n; i++) { array[i] = nextInt(); } return array; } } }