Leetcode #216 Combination Sum III

最新推荐文章于 2022-04-02 11:39:15 发布

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最新推荐文章于 2022-04-02 11:39:15 发布

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本文介绍了一个中等难度的编程问题：寻找所有可能的k个数的组合，这些数加起来等于给定的目标数n，且只能使用从1到9的数字。文章详细解释了如何通过回溯法解决这个问题，并给出了具体的代码实现。

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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]]

Credits

Difficulty: Medium

Easy practice on Backtracking.

class Solution {
public:
    vector<vector<int> >ans;
    void BackTracking(vector<int>& tempCom, int depth,int start, int target){
        if(depth==1){
            if(target<=9 && target>=start){
                tempCom.push_back(target);
                ans.push_back(tempCom);
                return;
            }
            else
                return;
        }
        if(start>=target||target<=0)
            return;
        
        for(int i = start;i<=min(9,target);i++){
            vector<int> temp = tempCom;
            temp.push_back(i);
            BackTracking(temp,depth-1,i+1,target-i);
        }
        return;
    }
    vector<vector<int> > combinationSum3(int k, int n) {
        vector<int> nums;
        BackTracking(nums,k,1,n);
        return ans;
    }
};