Combination Sum

39、combination sum1

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: 

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

class Solution {
public:
void search(vector<int>&candidates,int next,vector<int>&tmp,vector<vector<int>>&result,int target)
{
if(target==0)
{
result.push_back(tmp);
return;
}
if(next==candidates.size()||target-candidates[next]<0)
return;
tmp.push_back(candidates[next]);
search(candidates,next,tmp,result,target-candidates[next]);
tmp.pop_back();
search(candidates,next+1,tmp,result,target);
}
vector<vector<int>> combinationSum(vector<int>& candidates, int target) {
vector<int>tmp;
vector<vector<int>>result;
sort(candidates.begin(),candidates.end());//注意这一步
search(candidates,0,tmp,result,target);
return result;
}
};

40. Combination Sum II

Given a collection of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.

Each number in C may only be used once in the combination.

Note:

• All numbers (including target) will be positive integers.
• The solution set must not contain duplicate combinations.

 

For example, given candidate set [10, 1, 2, 7, 6, 1, 5] and target 8, 
A solution set is: 

[
  [1, 7],
  [1, 2, 5],
  [2, 6],
  [1, 1, 6]
]

class Solution {
public:
void search(vector<int>&candidates,int next,vector<int>&tmp,vector<vector<int>>&result,int target)
{
if(target==0)
{
result.push_back(tmp);
}
else
{
for(int i=next;i<candidates.size();i++)
{
if(candidates[i]>target)
return;
if(i&&candidates[i]==candidates[i-1]&&i>next)
continue;
tmp.push_back(candidates[i]);
search(candidates,i+1,tmp,result,target-candidates[i]);
tmp.pop_back();

}
}
}
vector<vector<int>> combinationSum2(vector<int>& candidates, int target) {
vector<int>tmp;
vector<vector<int>>result;
sort(candidates.begin(),candidates.end());//注意这一步
search(candidates,0,tmp,result,target);
return result;
}
};