# How to solve K sum problem

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2/5/20241 min read

The K Sum problem is a generalization of the Two Sum problem, where instead of finding two numbers that sum up to a target, you need to find k numbers that sum up to a target. Here's an explanation of how to solve the K Sum problem in Java:

**kSum method:**This method is the entry point for solving the K Sum problem.

It takes three parameters: the input array nums, the target sum target, and the value of k, which represents the number of elements that should sum up to the target.

First, it sorts the input array nums in ascending order. Sorting helps in using the two pointers technique efficiently.

Then, it calls the helper method kSumHelper with the sorted array, target sum, and other necessary parameters.

Finally, it returns the result obtained from the helper method.

**kSumHelper method:**This method is a recursive function that computes K Sum combinations.

It takes four parameters: the sorted input array nums, the target sum target, the value of k, and the start index, which indicates the starting position for considering elements in the array.

The method first initializes an empty list result to store the final K Sum combinations.

If k is equal to 2 (the base case for Two Sum), it uses the two pointers technique to find pairs of numbers that sum up to the target.

If k is greater than 2 (the recursive case), it iterates through the array, fixing one element at a time (nums[i]).

For each fixed element, it recursively solves the problem for k - 1 by calling kSumHelper with updated parameters.

It skips duplicates to avoid duplicate combinations by checking if the current element is the same as the previous one.

Finally, it returns the list result containing all valid K Sum combinations.