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]
思路
深搜，注意这类代码的一般格式。
1 void search(vector<vector<int> > &result, vector<int> &tmp, vector<int> &candidates, int index, int target){ 2 int n = candidates.size(); 3 if(index >= n) 4 return; 5 while(index+1 < n && candidates[index] == candidates[index+1]){ 6 index++; 7 } 8 if(target == 0){ 9 result.push_back(tmp); 10 return; 11 } 12 if(target < candidates[index]) 13 return; 14 search(result, tmp, candidates, index+1, target); 15 tmp.push_back(candidates[index]); 16 search(result, tmp, candidates, index, target-candidates[index]); 17 tmp.erase(tmp.end()-1); 18 } 19 vector<vector<int> > combinationSum(vector<int> &candidates, int target) { 20 // Start typing your C/C++ solution below 21 // DO NOT write int main() function 22 vector<vector<int> > result; 23 vector<int> tmp; 24 sort(candidates.begin(), candidates.end()); 25 search(result, tmp, candidates, 0, target); 26 return result; 27 }