Combination Sum

Desicription

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:

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[
[7],
[2, 2, 3]
]

Solution

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class Solution {
private:
vector<int> tmp;
vector<vector<int> > res;
public:
vector<vector<int>> combinationSum(vector<int>& candidates, int target) {
sort(candidates.begin(), candidates.end());
dfs(candidates, target, 0);
return res;
}
void dfs(vector<int>& candidates, int target, int index){
if(index == candidates.size())
return ;
int sum = 0;
for(int i = 0; i < tmp.size(); i++)
sum += tmp[i];
if(sum == target){
res.push_back(tmp);
return ;
}
else if(sum > target)
return ;
else{
for(int i = index; i < candidates.size(); i++){
tmp.push_back(candidates[i]);
dfs(candidates, target, i);
tmp.pop_back();
}
}
}
};