笛卡尔积概念及实现

定义：
设A,B为集合，用A中元素为第一元素，B中元素为第二元素构成的有序对，所有这样的有序对组成的集合




__author__ = 'root'

import itertools

left = [[1, 1, 1], [1, 2, 2], [2, 2, 1]]
right = [[1, 2, 2], [1, 3, 2], [2, 2, 1]]
for x in itertools.product(left, right):
    print x[0] + x[1]

运行结果：
/usr/bin/python2.7 /codes/python/PPro/Product.py
[1, 1, 1, 1, 2, 2]
[1, 1, 1, 1, 3, 2]
[1, 1, 1, 2, 2, 1]
[1, 2, 2, 1, 2, 2]
[1, 2, 2, 1, 3, 2]
[1, 2, 2, 2, 2, 1]
[2, 2, 1, 1, 2, 2]
[2, 2, 1, 1, 3, 2]
[2, 2, 1, 2, 2, 1]

Process finished with exit code 0

python对集合的操作还真是简洁~

package proj;

import java.util.ArrayList;
import java.util.List;

public class Product {

    public static void main(String[] args) {
        List<Integer> left = new ArrayList<Integer>();
        List<Integer> right = new ArrayList<Integer>();
        left.add(1);
        left.add(2);
        left.add(3);

        right.add(4);
        right.add(5);
        right.add(6);
        
        for (Integer l : left) {
            for (Integer r : right) {
                System.out.println(l + " " + r);
            }
        }
    }

}


result:
1 4
1 5
1 6
2 4
2 5
2 6
3 4
3 5
3 6