java实现笛卡尔积算法

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private static void descartes(List<List<String>> dimvalue, List<List<String>> result, int layer, List<String> curList) {        if (layer < dimvalue.size() - 1) {            if (dimvalue.get(layer).size() == 0) {                descartes(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));                    descartes(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);                }            }        }    }

public static void main(String[] args) {            List<List<String>> list = new ArrayList<List<String>>();            List<String> listSub1 = new ArrayList<String>();            List<String> listSub2 = new ArrayList<String>();            List<String> listSub3 = new ArrayList<String>();            listSub1.add("1");            listSub1.add("2");            listSub2.add("3");            listSub2.add("4");            listSub3.add("a");            listSub3.add("b");            list.add(listSub1);            list.add(listSub2);            list.add(listSub3);            List<List<String>> result = new ArrayList<List<String>>();            descartes(list, result, 0, new ArrayList<String>());            System.out.println(JSON.toJSONString(result));    }

运行结果：

[["1","3","a"],["1","3","b"],["1","4","a"],["1","4","b"],["2","3","a"],["2","3","b"],["2","4","a"],["2","4","b"]]

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