标签：positive note tmp numbers array add ret sed integer
Find all possible combinations of k numbers that add up to a number n, given that only numbers from 1 to 9 can be used and each combination should be a unique set of numbers.
Note:
Example 1:
Input: k = 3, n = 7 Output: [[1,2,4]]
Example 2:
Input: k = 3, n = 9 Output: [[1,2,6], [1,3,5], [2,3,4]]
题目大意：
给定1到9这九个数字，从中选取k个数字，使得这k个数字之和等于n。这k个数字的选择不能重复。
解法：
采用dfs做：
java:
class Solution {
List<List<Integer>>res;
private void dfs(int k,int n,int index,List<Integer>tmpSum){
if(n<0) return;
if(k==0){
if(n==0) res.add(new ArrayList<>(tmpSum));
return;
}
for(int i=index;i<10;i++){
tmpSum.add(i);
dfs(k-1,n-i,i+1,tmpSum);
tmpSum.remove(tmpSum.size()-1);
}
}
public List<List<Integer>> combinationSum3(int k, int n) {
res=new ArrayList();
List<Integer>tmpSum=new ArrayList<>();
dfs(k,n,1,tmpSum);
return res;
}
}
leetcode [216]Combination Sum III
标签：positive note tmp numbers array add ret sed integer
原文地址：https://www.cnblogs.com/xiaobaituyun/p/10789001.html
