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Leetcode 40. Combinations 2 solution using backtracking
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class Solution { | |
private: | |
vector<int> combination; | |
vector<vector<int>> combinations; | |
public: | |
vector<vector<int>> combinationSum2(vector<int>& candidates, int target) { | |
sort(candidates.begin(), candidates.end()); | |
explore(candidates, 0, target); | |
return combinations; | |
} | |
void explore(vector<int>& candidates, int start, int target){ | |
if(target == 0){ | |
combinations.push_back(combination); | |
return; | |
} | |
if(target < 0) return; | |
for(int i = start; i < candidates.size(); i++){ | |
if(i > start && candidates[i] == candidates[i-1]) continue; // skip duplicates | |
// explore all solutions using candidates[i] exactly once | |
combination.push_back(candidates[i]); | |
explore(candidates, i+1, target - candidates[i]); | |
// explore solutions that don't use candidates[i] | |
combination.pop_back(); | |
} | |
} | |
}; |
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