leetcode之Combination Sum

最新推荐文章于 2025-08-13 22:03:49 发布

原创最新推荐文章于 2025-08-13 22:03:49 发布 · 162 阅读

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#leetcode #算法 #面试

本文介绍了一种递归回溯算法解决组合求和问题的方法。该算法从候选数字集合中找出所有可能的组合，使这些组合中的数字之和等于目标数字。文章详细解释了递归搜索过程，并给出了具体实例。

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题目：

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]

解答：

直接进行递归回溯即可，可以用剩下的未满足的数量作为参数，可以减少存储，注意在递归的过程中进行剪枝

class Solution {
public:
    void search(int i,vector<int>& nums, int target, vector<int> temp)
    {
        if(0 == target)
        {
            res.push_back(temp);
            //temp.pop_back();
            return;
        }
        if(i == nums.size())
            return;
        if(nums[i] > target)
            return;
        while(target >= 0)
        {
            search(i + 1, nums,target, temp);
            temp.push_back(nums[i]);
            target -= nums[i];
        }
        
    }
    vector<vector<int>> combinationSum(vector<int>& candidates, int target) {
        vector<int> temp;
        sort(candidates.begin(),candidates.end());
        search(0, candidates, target, temp);
        return res;
        }
    
private:
    vector<vector<int>> res;
};