蓝桥杯（3.2）

1209. 带分数

import java.io.*; public class Main { static BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); static PrintWriter pw = new PrintWriter(new OutputStreamWriter(System.out)); static final int N = 10; static int n, cnt; static int[] a = new int[N]; static boolean[] st = new boolean[N]; public static int calc(int l, int r) { int res = 0; for (int i = l; i <= r; i ++ ) res = res * 10 + a[i]; return res; } public static void dfs(int u) { if (u > 9) { for (int i = 1; i <= 7; i ++ ) for (int j = i + 1; j <= 8; j ++ ) { int a = calc(1, i), b = calc(i + 1, j), c = calc(j + 1, 9); if (a * c + b == c * n) cnt ++ ; } return; } for (int i = 1; i <= 9; i ++ ) if (!st[i]) { a[u] = i; st[i] = true; dfs(u + 1); a[u] = 0; st[i] = false; } } public static void main(String[] args) throws IOException { n = Integer.parseInt(br.readLine()); dfs(1); pw.print(cnt); pw.flush(); pw.close(); } }

717. 简单斐波那契

import java.util.Scanner; public class Main { public static void main(String[] args) { Scanner sc = new Scanner(System.in); int n = sc.nextInt(); int f1 = 0; int f2 = 1; for(int i=1;i<=n;i++) { int f3 = f1 + f2; System.out.print(f1+" "); f1 = f2; f2 = f3; } } }

P1255 数楼梯

import java.math.BigInteger; import java.util.Scanner; public class Main { static BigInteger f1 = new BigInteger("1"); static BigInteger f2 = new BigInteger("2"); static BigInteger f3 = new BigInteger("0"); public static void main(String[] args) { Scanner sc = new Scanner(System.in); int n = sc.nextInt(); //1 2 3 5 ... if (n == 1) { System.out.println(f1); } else if (n == 2) { System.out.println(f2); } else { for (int i = 3; i <= n; i++) { f3 = f1.add(f2); f1 = f2; f2 = f3; } System.out.println(f3); } } }

P1036 [NOIP2002 普及组] 选数

import java.util.Scanner; public class Main { static int n; static int m; static final int N = 21; static int[] a = new int[N]; static int[] b = new int[N]; static int ans; public static boolean isPrime(int n) { for(int i=2;i<n;i++) { if(n%i == 0) return false; } return true; } public static void dfs(int u,int start) { if(u > m) { int sum = 0; for(int i=1;i<=m;i++) { sum+=b[i]; } if(isPrime(sum)) { ans++; } return ; } for(int i=start;i<=n;i++) { b[u] = a[i]; dfs(u+1,i+1); b[u] = 0; } } public static void main(String[] args) { Scanner sc = new Scanner(System.in); n = sc.nextInt(); m = sc.nextInt(); for(int i=1;i<=n;i++) { a[i] = sc.nextInt(); } dfs(1,1); System.out.println(ans); } }

P1028 [NOIP2001 普及组] 数的计算

import java.util.Scanner; public class Main{ //6 public static int dfs(int x) { if (x == 1) { return 1; } int tot = 1;//long for (int i = 1; i <= x / 2; i++) { tot += dfs(i); } return tot; } public static void main(String[] args){ Scanner sc = new Scanner(System.in); int n = sc.nextInt(); System.out.println(dfs(n)); } }

P1464 Function

import java.util.Scanner; public class Main { static int N = 21; static long[][][] s = new long[N][N][N]; public static long w(long a,long b,long c) { if(a<=0||b<=0||c<=0) return 1; if(a>20||b>20||c>20) return s[20][20][20]; if(a<b&&b<c) return s[(int)a][(int)b][(int)c-1]+s[(int)a][(int)b-1][(int)c-1]-s[(int)a][(int)b-1][(int)c]; return s[(int)a-1][(int)b][(int)c]+s[(int)a-1][(int)b-1][(int)c]+s[(int)a-1][(int)b][(int)c-1]-s[(int)a-1][(int)b-1][(int)c-1]; } public static void main(String[] args) { Scanner sc = new Scanner(System.in); long a,b,c; for(int i=0;i<=20;i++) for(int j=0;j<=20;j++) for(int k=0;k<=20;k++) s[i][j][k] = w(i,j,k); // 输入a、b、c，计算w(a, b, c)并输出结果 while (true) { a = sc.nextLong(); b = sc.nextLong(); c = sc.nextLong(); if (a == -1 && b == -1 && c == -1) return ; else System.out.println("w(" + a + ", " + b + ", " + c + ") = " + w(a, b, c)); } } }