50道编程题值04:将一个正整数分解质因数

package com.demo;

import java.util.*;

/**
* Created by 莫文龙 on 2018/3/26.
*/

//将一个正整数分解质因数。例如:输入 90 : 打印 90 = 2 * 3 * 3 * 5

public class Demo4 {

public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int num = scanner.nextInt();
if (num == 1) System.out.print(1);
int a = num;
ArrayList<Integer> list = new ArrayList<>();
for (int i = 2 ; i <= num ; i ++) {
if (num % i == 0) {
list.add(i);
num = num / i;
i = 1;
}
}
if (list.size() == 1) {
System.out.print(1 + "*" + a);
return;
}
for (int i = 0 ; i < list.size() - 1 ; i ++) {
System.out.print(list.get(i) + "*");
}
System.out.println(list.get(list.size() - 1));
}

}