【leetcode】Combination Sum
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]
1 class Solution { 2 3 public: 4 5 vector<vector<int> > combinationSum(vector<int> &candidates, int target) { 6 7 8 9 sort(candidates.begin(),candidates.end()); 10 11 vector<vector<int> > result; 12 13 vector<int> tmp; 14 15 16 17 backtracking(result,candidates,target,tmp,0,0); 18 19 20 21 return result; 22 23 } 24 25 26 27 void backtracking(vector<vector<int> > &result,vector<int> &candidates, int &target,vector<int> tmp, int sum,int index) 28 29 { 30 31 32 33 if(sum==target) 34 35 { 36 37 result.push_back(tmp); 38 39 return; 40 41 } 42 43 else 44 45 { 46 47 int sum0=sum; 48 49 //注意index 50 51 for(int i=index;i<candidates.size();i++) 52 53 { 54 55 tmp.push_back(candidates[i]); 56 57 sum=sum0+candidates[i]; 58 59 if(sum>target) 60 61 { 62 63 break; 64 65 } 66 67 backtracking(result,candidates,target,tmp,sum,i); 68 69 tmp.pop_back(); 70 71 } 72 73 } 74 75 } 76 77 };