help with backtracking in JAVA

Question

hello, im not so sure how to do this.
like in this Q:

Given an array of ints, is it possible to choose a group of some of the ints, beginning at the start index, such that the group sums to the given target? However, with the additional constraint that all 6's must be chosen. (No loops needed.)

i know tha base but i dont know how to add the constraint .
can someone show me the code that solve this problem so i can see how to do this kind of Q?
in JAVA,
Tnx a lot guys !

Answer 1

public class GroupSum {

public static boolean groupSum6(int start, int[] nums, int target) {
if (start >= nums.length) return target == 0;
if (nums[start] == 6) return groupSum6(start + 1, nums, target - 6);
return groupSum6(start + 1, nums, target - nums[start]) || groupSum6(start + 1, nums, target);
}

public static void main(String[] args) {
int[] nums = {6, 1, 2, 6, 4};
int target = 12;
System.out.println(groupSum6(0, nums, target)); // Output: true
}
}

Key Points:

• If the number is 6, it must be included in the sum.
• Recursively check both including or excluding each element.
• Base case: If we’ve gone through the array, check if the target is 0.

This is the solution that meets the constraints.