算法设计与应用基础系列9



Combination Sum

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: 

class Solution {public:    std::vector<std::vector<int> > combinationSum2(std::vector<int> &candidates, int target) {        std::sort(candidates.begin(), candidates.end());        std::vector<std::vector<int> > res;        std::vector<int> combination;        combinationSum2(candidates, target, res, combination, 0);        return res;    }private:    void combinationSum2(std::vector<int> &candidates, int target, std::vector<std::vector<int> > &res, std::vector<int> &combination, int begin) {        if (!target) {            res.push_back(combination);            return;        }        for (int i = begin; i != candidates.size() && target >= candidates[i]; ++i)            if (i == begin || candidates[i] != candidates[i - 1]) {                combination.push_back(candidates[i]);                combinationSum2(candidates, target - candidates[i], res, combination, i + 1);                combination.pop_back();            }    }};