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CombinationSum.java
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CombinationSum.java
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import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
public class CombinationSum {
public static List<List<Integer>> combinationSum(int[] candidates, int target) {
List<List<Integer>> res = new ArrayList<>();
List<Integer> tracker = new ArrayList<>();
//helper function
backtrack(candidates,0,target,tracker,res);
return res;
}
static void backtrack(int[] arr, int idx, int k, List<Integer> tracker, List<List<Integer>> res){
//base condition
if(idx== arr.length){
//if condition satisfies
if (k==0){
res.add(new ArrayList<>(tracker));
}
return;
}
//making choices
if (arr[idx]<=k){
//going forward with the choice
tracker.add(arr[idx]);
backtrack(arr,idx,k-arr[idx],tracker,res);
//removing the choice
tracker.remove(tracker.size()-1);
}
//going without the choice
backtrack(arr,idx+1,k,tracker,res);
}
public static void main(String[] args) {
int[] arr = {2,3,6,7};
System.out.println( combinationSum(arr,7));
}
}