计算笛卡尔积

此处借鉴一下别人的代码，还没有用过，等用过之后再来修改

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
 
/**
 * 循环和递归两种方式实现未知维度集合的笛卡尔积
 * Created on 2015-05-22
 * @author luweijie
 */
public class Descartes {
 
    /**
     * 递归实现dimValue中的笛卡尔积，结果放在result中
     * @param dimValue 原始数据
     * @param result 结果数据
     * @param layer dimValue的层数
     * @param curList 每次笛卡尔积的结果
     */
    private static void recursive (List<List<String>> dimValue, List<List<String>> result, int layer, List<String> curList) {
        if (layer < dimValue.size() - 1) {
            if (dimValue.get(layer).size() == 0) {
                recursive(dimValue, result, layer + 1, curList);
            } else {
                for (int i = 0; i < dimValue.get(layer).size(); i++) {
                    List<String> list = new ArrayList<String>(curList);
                    list.add(dimValue.get(layer).get(i));
                    recursive(dimValue, result, layer + 1, list);
                }
            }
        } else if (layer == dimValue.size() - 1) {
            if (dimValue.get(layer).size() == 0) {
                result.add(curList);
            } else {
                for (int i = 0; i < dimValue.get(layer).size(); i++) {
                    List<String> list = new ArrayList<String>(curList);
                    list.add(dimValue.get(layer).get(i));
                    result.add(list);
                }
            }
        }
    }
 
    /**
     * 循环实现dimValue中的笛卡尔积，结果放在result中
     * @param dimValue 原始数据
     * @param result 结果数据
     */
    private static void circulate (List<List<String>> dimValue, List<List<String>> result) {
        int total = 1;
        for (List<String> list : dimValue) {
            total *= list.size();
        }
        String[] myResult = new String[total];
 
        int itemLoopNum = 1;
        int loopPerItem = 1;
        int now = 1;
        for (List<String> list : dimValue) {
            now *= list.size();
 
            int index = 0;
            int currentSize = list.size();
 
            itemLoopNum = total / now;
            loopPerItem = total / (itemLoopNum * currentSize);
            int myIndex = 0;
 
            for (String string : list) {
                for (int i = 0; i < loopPerItem; i++) {
                    if (myIndex == list.size()) {
                        myIndex = 0;
                    }
 
                    for (int j = 0; j < itemLoopNum; j++) {
                        myResult[index] = (myResult[index] == null? "" : myResult[index] + ",") + list.get(myIndex);
                        index++;
                    }
                    myIndex++;
                }
 
            }
        }
 
        List<String> stringResult = Arrays.asList(myResult);
        for (String string : stringResult) {
            String[] stringArray = string.split(",");
            result.add(Arrays.asList(stringArray));
        }
    }
 
    /**
     * 程序入口
     * @param args
     */
    public static void main (String[] args) {
        List<String> list1 = new ArrayList<String>();
        list1.add("1");
        list1.add("2");
 
        List<String> list2 = new ArrayList<String>();
        list2.add("a");
        list2.add("b");
 
        List<String> list3 = new ArrayList<String>();
        list3.add("3");
        list3.add("4");
        list3.add("5");
 
        List<String> list4 = new ArrayList<String>();
        list4.add("c");
        list4.add("d");
        list4.add("e");
 
        List<List<String>> dimValue = new ArrayList<List<String>>();
        dimValue.add(list1);
        dimValue.add(list2);
        dimValue.add(list3);
        dimValue.add(list4);
 
        List<List<String>> recursiveResult = new ArrayList<List<String>>();
        // 递归实现笛卡尔积
        recursive(dimValue, recursiveResult, 0, new ArrayList<String>());
 
        System.out.println("递归实现笛卡尔乘积: 共 " + recursiveResult.size() + " 个结果");
        for (List<String> list : recursiveResult) {
            for (String string : list) {
                System.out.print(string + " ");
            }
            System.out.println();
        }
 
        List<List<String>> circulateResult = new ArrayList<List<String>>();
        circulate(dimValue, circulateResult);
        System.out.println("循环实现笛卡尔乘积: 共 " + circulateResult.size() + " 个结果");
        for (List<String> list : circulateResult) {
            for (String string : list) {
                System.out.print(string + " ");
            }
            System.out.println();
        }
    }
}