Blue Bridge Cup test questions basic exercises decomposition prime factor BASIC-16 JAVA

Foreword

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Exam questions basic exercises to decompose prime factors

Resource limit
Time limit: 1.0s Memory limit: 512.0MB

Problem description
　　Find the prime factorization of all integers in the interval [a, b].

Input format
　　Input two integers a, b.

Output format
　　Each line outputs a number of decompositions, the form is k = a1 a2 a3 ... (a1 <= a2 <= a3 ..., k is also from small to large) (see the example for details)

Sample input
3 10

Sample output
3 = 3
4 = 2 2
5 = 5
6 = 2 3
7 = 7
8 = 2 2 2
9 = 3 3
10 = 2 5

Tip
　　first sieve out all prime numbers, and then decompose.

Data scale and convention
　　2 <= a <= b <= 10000

Code for this question

import java.util.Scanner;

public class PrimeDecomposition {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int[] array = new int[b - a + 1];
        if (a == b)
            array[0] = a;
        else
            for (int i = a, j = 0; i <= b; i++, j++)
                array[j] = i;
        for (int value : array) {
            StringBuffer st = new StringBuffer(value + "=");
            int z = 2;
            while (z <= value) {
                if (value % z == 0) {
                    if (st.charAt(st.length() - 1) != '=') st.append("*");
                    st.append(z);
                    value = value / z;
                    z = 2;
                } else
                    z++;
            }
            System.out.println(st);
        }
    }
}