(组合数学3.3.2.2)UVA 10497 - Sweet Child Makes Trouble(特殊的排列问题——错排方案数)

package com.njupt.acm;import java.math.BigInteger;import java.util.Scanner;public class UVA_10497 {public static void main(String[] args) {BigInteger d[] = new BigInteger[805];d[1] = new BigInteger("0");d[2] = new BigInteger("1");int i;for(i = 3 ; i <= 801 ; ++i){d[i] = new BigInteger((i - 1) + "").multiply(d[i-2].add(d[i-1]));}Scanner scanner = new Scanner(System.in);int n ;while(true){n =  scanner.nextInt();if(n < 0){break;}System.out.println(d[n]);}}}