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【LeetCode算法练习(C++)】Combination Sum

程序员文章站 2022-05-21 22:38:49
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题目:
Given a set of candidate numbers (C) (without duplicates) 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.
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]
]

链接:Combination Sum
解法:先对数组排序,递归遍历,将正确的解添加到返回数组中。时间O(n^2)

class Solution {
public:
    vector<vector<int> > combinationSum(vector<int> &candidates, int target) {
        vector<vector<int> > ans;
        vector<int> out;
        sort(candidates.begin(), candidates.end());
        combinationSumDFS(candidates, target, 0, out, ans);
        return ans;
    }
    void combinationSumDFS(vector<int> &candidates, int target, int start, vector<int> &out, vector<vector<int> > &res) {
        if (target < 0) return;
        else if (target == 0) res.push_back(out);
        else 
            for (int i = start; i < candidates.size(); ++i) {
                out.push_back(candidates[i]);
                combinationSumDFS(candidates, target - candidates[i], i, out, res);
                out.pop_back();
            }
    }
};

Runtime: 13 ms

相关标签: leetcode c++