组合总和

package demo10;

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

/**
 * @author xianyu
 * @version 1.0
 * @date 2020/4/25 15:16
 * 组合总和
 * 给定一个无重复元素的数组 candidates 和一个目标数 target ，找出 candidates 中所有可以使数字和为 target 的组合。
 * candidates 中的数字可以无限制重复被选取。
 */
public class CombinationSum {

    public static void main(String[] args) {

        int[] candidates = new int[]{2,3,6,7};
        int target = 7;
        Arrays.sort(candidates);
        List<List<Integer>> result =  combinationSum(candidates, target);
        System.out.println(result.toString());
    }

    public static List<List<Integer>> combinationSum(int[] candidates,int target){
        List<List<Integer>> result = new ArrayList<>();
        List<Integer> list = new ArrayList<>();
        if (candidates == null || candidates.length == 0)
            return result;
        dfs(candidates,target,0,list,result);
        return result;
    }

    public static void dfs(int[] candidates,int target,int start,List<Integer> list,List<List<Integer>> result){
        if(target == 0){
            result.add(new ArrayList<>(list));
            return;
        }

        for (int i = start; i < candidates.length; i++) {
            if(candidates[i]<=target){
                list.add(candidates[i]);
                dfs(candidates,target-candidates[i],i,list,result);
                list.remove(list.size()-1);
            }
        }
    }


}