演算法-Java組合

標籤：private   reac   .com   AC   ret   stl   clear   single   select   

code:

import org.assertj.core.util.Lists;import java.util.ArrayList;import java.util.Collections;import java.util.List;/** * 52523243 * * @param <E> */public class Combine<E> {    private List<List<E>> resList = Lists.newArrayList();    public List<List<E>> combine(List<E> srcList, int require) {        resList.clear();        if (require < 0) {            throw new IllegalArgumentException("");        }        if (srcList == null || srcList.size() == 0) {            return Lists.newArrayList();        }        if (require == 1) {            srcList.forEach(src -> resList.add(Collections.singletonList(src)));            return resList;        }        if (require == srcList.size()) {            return resList = Collections.singletonList(srcList);        }        combinerSelect(srcList, new ArrayList<>(), srcList.size(), require);        return resList;    }    private void combinerSelect(List<E> srcList, List<E> workSpace, int n, int require) {        List<E> copyData;        List<E> copyWorkSpace;        if (workSpace.size() == require) {            List<E> newL = Lists.newArrayList();            newL.addAll(workSpace);            resList.add(newL);        }        for (int i = 0; i < srcList.size(); i++) {            copyData = new ArrayList<>(srcList);            copyWorkSpace = new ArrayList<>(workSpace);            copyWorkSpace.add(copyData.get(i));            for (int j = i; j >= 0; j--) {                copyData.remove(j);            }            combinerSelect(copyData, copyWorkSpace, n, require);        }    }}

test:

import com.y.Combine;import org.assertj.core.util.Lists;import org.junit.Test;import java.util.List;public class CombineTest {    @Test    public void test_combine() {        Combine<String> combine = new Combine<>();        List<String> testList = Lists.newArrayList("a", "b", "c", "d", "e");        List<List<String>> res = combine.combine(null, 3);        System.out.println(res);        res = combine.combine(Lists.newArrayList(), 3);        System.out.println(res);        res = combine.combine(testList, 1);        System.out.println(res);        res = combine.combine(testList, 3);        System.out.println(res);        res = combine.combine(testList, 5);        System.out.println(res);//        res = combine.combine(testList, -1);//        System.out.println(res);    }}

演算法-Java組合