题例：将一个正整数拆分成若干个正整数的和(来自一名招聘者的灵魂拷问)

题例：将一个正整数拆分成若干个正整数的和
第一次写这种算法，大概花了快两个小时吧。

来自一名招聘者的灵魂拷问，第一次写，写了好久。先不说了上代码。
方法一：
package com.twelve.test;

import java.util.HashSet;
import java.util.Scanner;
import java.util.Set;

/**

• @author 武
  *2019年7月18日15:36:27
  */
  public class Demo02 {

  public static void main(String[] args) {
  Scanner scanner = new Scanner(System.in);
  int n = scanner.nextInt();
  System.out.println(toStr(calc(n)));
  }

  public static Set calc(int n) {
  Set possibility = new HashSet();
  Composition composition = new Composition();
  switch (n) {
  case 1:
  composition.add(1);
  possibility.add(composition);
  return possibility;
  case 2:
  composition.add(1);
  composition.add(1);
  possibility.add(composition);
  return possibility;
  default:
  for (int i = 1; i <= n / 2; i++) {
  composition = new Composition();
  composition.add(i);
  composition.add(n - i);
  possibility.add(composition);
  if (i <= n - i) {
  Set partial_pos = calc(n - i);
  for (Composition pos : partial_pos) {
  pos.add(i);
  possibility.add(pos);
  }
  }
  }
  return possibility;
  }
  }

  public static String toStr(Set possibility) {
  String str = "total : " + possibility.size() + “\n”;
  for (Composition pos : possibility)
  str += toStr(pos);
  return str;
  }

  public static String toStr(Composition composition) {
  String str = composition.get(0) + “”;
  for (int i = 1; i < composition.size(); i++)
  str += (" + " + composition.get(i));
  str += “\n”;
  return str;
  }

}

package com.twelve.test;

import java.util.ArrayList;
import java.util.Collections;

/**

• @author 武
  *2019年7月18日15:47:27
  */
  public class Composition extends ArrayList {
  @Override
  public boolean equals(Object other) {
  Composition comp = (Composition) other;
  Collections.sort(this);
  Collections.sort(comp);
  if (this.isEmpty() || comp.isEmpty() || this.size() != comp.size())
  return false;
  for (int i = 0; i < this.size(); i++) {
  if (this.get(i) != comp.get(i))
  return false;
  }
  return true;
  }

  @Override
  public int hashCode() {
  return 0;
  }
  }

++++++++++++++++++++++++++++++++++++++++++++++++++++++++
此上该程序已写完。

方法二：
下面试刚听到例题之后的理解，当然 也可以实现，不过需要修改程序，增加输出即可。此方法比较繁琐，不适用于正式开发程序，望谨记，仅供参考。
package com.twelve.test;

import java.util.Random;
import java.util.Scanner;

/**

• @author 武 2019年7月18日15:32:00
  */
  public class Demo01 {

  public static int[] getNL(int number, int size, int[] a) {

   Random rand = new Random();
   a = new int[size];
   for (int i = 0; i < size - 1; i++) {
   	int x = rand.nextInt(number);// 10以内，不填值默认为int类型之内
   	number = number - x;
   	a[i] = x;
   }
   a[size - 1] = number;// 最后一个值，应该是前面随机之后，算出来的
   return a;
  

  }

  public static void main(String[] args) {
  Scanner scanner = new Scanner(System.in);
  int a[] = null;
  int b[] = null;
  int c[] = null;
  int d[] = null;
  int number = scanner.nextInt();
  int size = scanner.nextInt();
  a = getNL(number, size, a);
  b = getNL(number, size, b);
  for (int i = 0; i < number; i++) {
  c = getNL(number, size, c);
  d = getNL(number, size, d);
  }

   for (int i : a) {
   	System.out.print(i + "-");
   }
   System.out.println("****");
   for (int i : b) {
   	System.out.print(i + "-");
   }
   System.out.println("****");
   for (int i : c) {
   	System.out.print(i + "-");
   }
   System.out.println("****");
   for (int i : d) {
   	System.out.print(i + "-");
   }
   System.out.println("****");
  

  }

}

控制台可以输出，测试，代码方面仅供参考，所有解释权谨归作者所有。