问题描述

力扣https://leetcode.cn/problems/Ygoe9J/

解题思路

实例代码

class Solution {
    private LinkedList<List<Integer>>res=new LinkedList<>();
    private LinkedList<Integer>data=new LinkedList<>();
    private int sum=0;
    public List<List<Integer>> combinationSum(int[] candidates, int target) {
        reverse(candidates,target,0);
        return res;
    }
    public void reverse(int []candidates,int target,int index){
        //递归出口
        if(index==candidates.length){
            return;
        }
        if(target==0){
            res.add(new LinkedList(data));
            return;
        }
        //不选择当前数字
        reverse(candidates,target,index+1);
        //选择当前数字
        if(target-candidates[index]>=0){
            data.add(candidates[index]);
            reverse(candidates,target-candidates[index],index);
            //回溯
            data.removeLast();
        }
      
    }
}

问题描述

力扣https://leetcode.cn/problems/4sjJUc/

解题思路

实例代码

class Solution {
    private LinkedList<List<Integer>>res=new LinkedList<>();
    private LinkedList<Integer>data=new LinkedList<>();
    public List<List<Integer>> combinationSum2(int[] candidates, int target) {
        Arrays.sort(candidates);
        reverse(candidates,0,target);

        return res;
    }
    public void reverse(int[]candidates,int index,int target){
        if(target==0){
                res.add(new LinkedList(data));
                return;
            }
          for(int i=index;i<candidates.length;++i){
              if(candidates[i]>target){
                  break;
              }
              if(i>index&&candidates[i]==candidates[i-1]){
                  continue;
              }
              data.add(candidates[i]);
              reverse(candidates,i+1,target-candidates[i]);
              data.removeLast();
          }
    }
}