qingbo777 wrote:
晕.楼上的把我弄糊涂了.特地查了一下书.
N的阶乘公式:
N!=1*2*3*....(N-2)*(N-1)*N 且规定0!=1 1!=1
Eg:8!=1*2*3*4*5*6*7*8

int N=you give it to me;
if(N==0){
        N=1;
}else{
        for(int i=1;i<N;i++){
                N=N*i;
        }
}
return N;

littledeer1974 wrote:
啊,好象我弄错了,不好意思,规定0!=1 1!=1 是对的,我说的是错的

int N=you give it to me;
if(N==0){
        N=1;
}else{
        for(int i=1;i<N;i++){
                N=N*i;
        }
}
return N;

这回怎么样呢

别看问题简单,就抓我这粗心的人

littledeer1974 wrote:
恩,for的判断应该是i<=N是对的,
关于存放的结果,应该可以的吧,当然你的写法比较简单明了,也很正统

  public static String getJieCheng(int n) throws Exception{
    if(n<0)throw new Exception("Error input");
    BigInteger result = new BigInteger("1");
    if (n == 0 || n == 1) {
      return result.toString();
    }
    for (int i = 1; i <= n; i++) {
      BigInteger b = new BigInteger(Integer.toString( i ));
      result = result.multiply( b );
    }
    return result.toString();
  }

import java.math.BigInteger;

public class kavinjiecheng {
  kavinjiecheng() {
    super();
  }

  public static String getJieCheng(int n) throws Exception {
    if (n < 0)
      throw new Exception("Error input");
    BigInteger result = new BigInteger("1");
    if (n == 0 || n == 1) {
      return result.toString();
    }
    for (int i = 1; i <= n; i++) {
      BigInteger b = new BigInteger(Integer.toString(i));
      result = result.multiply(b);
    }
    return result.toString();
  }

  public static void main(String[] args) {
    try {
      System.out.println(getJieCheng(5000));
    } catch (Exception e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    }
  }
}

import java.io.*;

public class FactorialDemo {
  public static void main(String[] args) {
    System.out.println(String.valueOf(factorial(4)));
  }
  
  static int factorial(int n) {
    int tmp = 0;
    
    if (n == 0 || n == 1) {
      tmp = 1;
    }else if (n > 1) {
      tmp = n * factorial(n - 1);
    }
    
    return tmp;
  }
}