[LeetCode] Combination Sum

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]

以下是我 AC 的代码：

/** * author:Zhou Jianxin */

class Solution { public: vector<vector<int> > combinationSum(vector<int> &candidates, int target) { sort(candidates.begin(), candidates.end()); vector<vector<int>> ret; vector<int> path; combinationSumRec(candidates, target, ret, path, 0); return ret; } private: void combinationSumRec(const vector<int> &candidates, int target, vector<vector<int>> &ret, vector<int> &path, size_t index) { if (target == 0) { ret.push_back(path); return; } int prev = -1; for (size_t ix = index; ix != candidates.size(); ++ix) { if (candidates[ix] > target) { return; } if (candidates[ix] == prev) { continue; } path.push_back(candidates[ix]); combinationSumRec(candidates, target - candidates[ix], ret, path, ix); path.erase(path.end() - 1); prev = candidates[ix]; } } };