# 39 Combination Sum – Medium

### Problem:

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]

### Thoughts:

Idea is to use a modified DFS.

### Solutions:

```java
public class Solution {
    public List<List<Integer>> combinationSum(int[] candidates, int target) {
        List<List<Integer>> result = new ArrayList<List<Integer>>();
        if(candidates == null || candidates.length == 0) return result;
        ArrayList<Integer> current = new ArrayList<Integer>();
        Arrays.sort(candidates);
        combinationSum(candidates, target, 0, current, result);
        return result;
    }
    public void combinationSum(int[] candidates, int target, int j, ArrayList<Integer> curr, List<List<Integer>> result){
        if(target == 0){
            ArrayList<Integer> temp = new ArrayList<Integer>(curr);
            result.add(temp);
            return;
        }
        for(int i=j; i<candidates.length; i++){
            if(target < candidates[i])
                return;
            curr.add(candidates[i]);
            combinationSum(candidates, target - candidates[i], i, curr, result);
            curr.remove(curr.size()-1);
       }//for i
   }//combinationSum
}//Solution
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://ugopireddy.gitbook.io/leet-code-solutions/solutions_1_-_50/39_combination_sum__medium.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.