入门算法 分解质因数算法 202001061516

package org.jimmy.autosearch.test;

import java.util.ArrayList;
import java.util.HashMap;

/**
 * 质因数分解练习,by:ラピスラズリ(Dawn)
 *
 */
public class PrimeFactorizationTest2019123101 {

    //1-1000以内的质数
    public static final int MAX_NUMBER = 1000;
    //1-100范围内的数质因数分解
    public static final int MAX_NUMBER2 = 100;
    //质数集合
    public static ArrayList<Integer> primeNumberList = new ArrayList<Integer>();
    //key:数字,value:被整除的数
    public static final HashMap<Integer, ArrayList<Integer>> map = new HashMap<Integer, ArrayList<Integer>>();
    //key:数字,value:被整除的质数(分解的质因数)
    public static final HashMap<Integer, ArrayList<Integer>> map2 = new HashMap<Integer, ArrayList<Integer>>();
    //积的初始值
    public static final int INITIAL_PRODUCT = 1;
    //质因数集合
    public static Integer product = 1;
    
    public static void main(String[] args) {
        try {
            test();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    
    public static void test() throws Exception{
        for(int i = 1; i <= MAX_NUMBER; i++){
            ArrayList<Integer> list = new ArrayList<Integer>();
            for(int j = 1; j <= i; j++){
                double value = (double)i / j;
                if(value % 1 == 0){
                    if(!map.containsKey(i)){
                        list.add(j);
                        map.put(i, list);
                    }else{
                        list = map.get(i);
                        map.remove(i);
                        list.add(j);
                        map.put(i, list);
                    }
                }
            }
        }
        //筛选出质数,只能被1和自己整除的数
        map.entrySet().forEach(entry -> {
            int count = entry.getValue().size();
            if(count == 2){
                primeNumberList.add(entry.getKey());
            }
        });
        //分解质因数
        for(int i = 1; i <= MAX_NUMBER2; i++){
            //跳过质数
            if(primeNumberList.contains(i)){
                continue;
            }
            test2(i, i);
        }
        //分解质因数整理:
        map2.entrySet().forEach(entry -> {
            ArrayList<Integer> list = entry.getValue();
            list = test5(entry.getKey(), list);
            entry.setValue(list);
        });
        //分解质因数结果:
        map2.entrySet().forEach(entry -> {
            ArrayList<Integer> list = entry.getValue();
            final StringBuffer expression = new StringBuffer();
            expression.append(entry.getKey() + "=");
            list.forEach(number -> {
                expression.append(number + "*");
            });
            expression.delete(expression.length() - 1, expression.length());
            System.out.println(expression);
        });
    }
    
    public static ArrayList<Integer> test5(int number, ArrayList<Integer> list){
//        System.out.println("number:" + number);
//        System.out.println(list.size());
        //计算所有质因数的乘积
        ArrayList<Integer> resultList = new ArrayList<Integer>();
        int value = 1;
        for(int i = 0; i < list.size(); i++){
            int currentNumber = list.get(i);
//            System.out.println("currentNumber:" + currentNumber + ",value:" + value);
            value *= currentNumber;
            if(value > number){
                break;
            }
            resultList.add(currentNumber);
        }
        return resultList;
    }
    
    public static void test3(){
        int count = 2;
        /*map2.entrySet().forEach(entry -> {
            Integer number = entry.getKey();
            ArrayList<Integer> list = entry.getValue();
            int value = 1;
            int index = 1;
            for(int i = 0; i < list.size(); i++){
                for(int j = i + index; j < list.size(); j++){
                    
                }
            }
        });*/
    }
    
    public static void test4(int max, int count, int index, int index2) throws Exception {
        for(int i = index2; i < max; i++){
            int tempIndex = 1;
            int tempIndex2 = i;
            int j = i + tempIndex;
            int k = i + tempIndex + 1;
            if(i >= max - 1 && j >= max - 1 && k >= max - 1){
                throw new RuntimeException();
            }
//            System.out.println("i:" + i + ",j:" + j + ",k:" + k);
            if(k >= max - 1){
                tempIndex = 0;
                tempIndex2++;
            }else{
                k++;
            }
            tempIndex++;
            if(i <= max - 1 && j <= max - 1){
                test4(max, count, tempIndex, tempIndex2);
            }
        }
    }
    
    public static void test2(int initialNumber, int number){
        for(int i = 0; i < primeNumberList.size(); i++){
            Integer primeNumber = primeNumberList.get(i);
            ArrayList<Integer> list = null;
            double value = (double)number / primeNumber;
//            System.out.println("number:" + number + ",primeNumber:" + primeNumber + ",value:" + value);
            if(value % 1 == 0 && value >= 1){
                if(!map2.containsKey(initialNumber)){
                    list = new ArrayList<Integer>();
                    list.add(primeNumber);
                    map2.put(initialNumber, list);
                }else{
                    list = map2.get(initialNumber);
                    map2.remove(initialNumber);
                    list.add(primeNumber);
                    map2.put(initialNumber, list);
                }
                int result = (int) value;
//                    System.out.println("initialNumber:" + initialNumber + ",p:" + product);
                test2(initialNumber, result);
            }
        }
    }
    
}

效果图:

 好了.