题目:
给出[2,2, 3,4,7],找出所有组合target = 7
example: [2,2,4]、[3,4]、[7]
/**
* Author:m
* Date: 2023/04/08 8:26
*/
public class Target7 {
private static final int TARGET = 7;
public static void main(String[] args) {
int[] array = new int[]{
2, 2, 3, 4, 7};
List<List<Integer>> result = dfs(array);
System.out.println(result);
}
private static List<List<Integer>> dfs(int[] array) {
if (array == null) {
return Lists.newArrayList();
}
List<List<Integer>> result = Lists.newArrayList();
List<Integer> combine = Lists.newArrayList();
int initIndex = 0;
int sum = 0;
recursion(result, combine, array, initIndex, sum);
return result;
}
private static void recursion(List<List<Integer>> result, List<Integer> combine, int[] array, int initIndex, Integer sum) {
// 1.终止条件
if (sum > TARGET) {
return;
}
// 2.小集合添加至大集合
if (sum == TARGET) {
result.add(Lists.newArrayList(combine));
return;//sum已经等于target了,以combine为基础的元素再去结合别的元素求和,只会越来越大于target,无需继续了
}
// 3.for循环
for (int i = initIndex; i < array.length; i++) {
// 3.1添加元素到小集合
combine.add(array[i]);
// 3.2递归(i+1)
recursion(result, combine, array, i +1, sum + array[i]);
// 3.3回溯(小集合删除最后一个元素)
combine.remove(combine.size() - 1);
}
}
}