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  • Combination Sum III

    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.

    Ensure that numbers within the set are sorted in ascending order.


    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]]

    思路:这道题和Combination Sum II的思路类似。只不过candidates数组里只有1-9这9个数,且增加了累加次数的限制。

     1 class Solution {
     2 public:
     3     void assist(vector<vector<int> >& res, vector<int>& cur, int target, int k, int st)
     4     {
     5         if (k == 0)
     6         {
     7             if (target == 0)
     8                 res.push_back(cur);
     9             return;
    10         }
    11         for (int i = st; i <= 9; i++)
    12         {
    13             cur.push_back(i);
    14             assist(res, cur, target - i, k - 1, i + 1);
    15             cur.pop_back();
    16         }
    17     }
    18     vector<vector<int>> combinationSum3(int k, int n) {
    19         vector<vector<int> > res;
    20         vector<int> cur;
    21         assist(res, cur, n, k, 1);
    22         return res;
    23     }
    24 };
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  • 原文地址:https://www.cnblogs.com/fenshen371/p/4953007.html
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