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]
利用递归搜索，同时剪枝就可以
class Solution {
public:
vector<vector<int> > combinationSum(vector<int> &candidates, int target) {
sort(candidates.begin(),candidates.end());
vector<vector<int> > result;
vector<int> tmp;
backtracking(result,candidates,target,tmp,,);
return result;
}
void backtracking(vector<vector<int> > &result,vector<int> &candidates, int &target,vector<int> tmp, int sum,int index)
{
if(sum==target)
{
result.push_back(tmp);
return;
}
else
{
int sum0=sum;
//注意index
for(int i=index;i<candidates.size();i++)
{
tmp.push_back(candidates[i]);
sum=sum0+candidates[i];
if(sum>target)
{
break;
}
backtracking(result,candidates,target,tmp,sum,i);
tmp.pop_back();
}
}
}
};