class Solution {
List<List<Integer>> lists = new ArrayList<>();
public List<List<Integer>> combinationSum(int[] candidates, int target) {
if(candidates == null && target <0 || candidates.length<0){
return null;
}
List<Integer> list = new ArrayList<>();
Core(0,candidates,target,list);
return lists;
}
public void Core(int start ,int[] candidates ,int target,List<Integer> list){
if(target <0){
return ;
}else if(target == 0){
lists.add(new ArrayList<>(list));
}else{
for(int i = start;i<candidates.length;++i){
list.add(candidates[i]);
Core(i,candidates,target-candidates[i],list);
list.remove(list.size()-1);
}
}
}
}
用到了回溯法, 别忘了剪枝,就是当前节点的值,小小于减去的值。
减去的值,不能比上一个减去的值少。