38_leetcode_Combination Sum

最新推荐文章于 2025-09-13 14:08:34 发布

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最新推荐文章于 2025-09-13 14:08:34 发布

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分类专栏： leetcode 算法编程文章标签： leetcode 算法编程语言面试 string

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本文介绍了一种寻找候选数集合中所有唯一组合的算法，这些组合的和等于目标数。文章详细阐述了处理特殊情况的方法、如何对数组进行排序、递归实现的步骤以及如何获取有效的组合结果。

Given a set of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.

The same repeated number may be chosen from C unlimited number of times.

Note:

All numbers (including target) will be positive integers.
Elements in a combination (a1, a2, … , ak) must be in non-descending order. (ie, a1 ≤ a2 ≤ … ≤ ak).
The solution set must not contain duplicate combinations.

For example, given candidate set 2,3,6,7 and target 7,
A solution set is:
[7]

[2, 2, 3]

1:特殊情况；2:对数组进行按升序列进行排序；3:采用递归的方式，注意递归结束的条件；4:获得满足提交的组合

    vector<vector<int> > combinationSum(vector<int> &candidates, int target) {
        vector<vector<int> > result;
        if(candidates.size() <= 0)
        {
            return result;
        }
        
        sort(candidates.begin(), candidates.end());
        
        vector<int> temp;
        combinationSumCore(candidates, target, 0, temp, result);
        
        return result;
    }
    
    void combinationSumCore(vector<int> &candidates, int target, int index, vector<int> &temp, vector<vector<int> > &result)
    {
        if(index == candidates.size() || candidates[index] > target)
        {
            return;
        }
        
        if(candidates[index] == target)
        {
            temp.push_back(candidates[index]);
            result.push_back(temp);
            temp.pop_back();
            return;
        }
        else
        {
            temp.push_back(candidates[index]);
            combinationSumCore(candidates, target - candidates[index], index , temp, result);
            temp.pop_back();
            combinationSumCore(candidates, target, index+1, temp, result);
        }
        
    }