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[Java] 蓝桥杯BASIC-16 基础练习分解质因数

问题描述

求出区间[a,b]中所有整数的质因数分解。

输入格式

输入两个整数a，b。

输出格式

每行输出一个数的分解，形如k=a1*a2*a3…(a1<=a2<=a3...，k也是从小到大的)(具体可看样例)

样例输入

3 10

样例输出

3=3

4=2*2

5=5

6=2*3

7=7

8=2*2*2

9=3*3

提示

先筛出所有素数，然后再分解。

数据规模和约定

2<=a<=b<=10000

package base16;
 
import java.util.Scanner;
 
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int a = in.nextInt();
        int b = in.nextInt();
        in.close();
 
        for (int i = a; i <= b; i++) {
            int temp = i;
            System.out.print(temp + "=");
            boolean flag = false;
            while (temp != 1) {
                //每次从小到大找，找到一个就求除数，然后重新开始找
                for (int j = 2; j <= temp; j++) {
                    if (isPrimer(j) && temp % j == 0) {
                        temp /= j;
                        if (flag) {
                            System.out.print("*");
                        }
                        System.out.print(j);
                        flag = true;
                        //break;
                    }
 
                }
 
            }
            System.out.println();
        }
    }
 
    //判断素数
    private static boolean isPrimer(int j) {
        if (j == 0) {
            return false;
        } else if (j == 2 || j == 3) {
            return true;
        } else {
            for (int i = 2; i < Math.sqrt(j * j); i++) {
                if (j % i == 0) {
                    return false;
                }
            }
        }
 
        return true;
    }
}

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