Hashing Algorithm Application | Dataford Interview Questions

How would you apply a hashing algorithm to solve a particular problem? Implement count_pairs(nums, target) to return the number of index pairs i < j whose values sum to target, counting duplicate values at different indices as separate pairs. The input is an integer list and an integer target, and the output is a nonnegative integer; use a hash-based approach rather than enumerating every pair.

Constraints

0 <= nums.length <= 10^5
-10^9 <= nums[i] <= 10^9
-2 * 10^9 <= target <= 2 * 10^9
Pairs are identified by indices, so duplicate values at different indices count separately

Function Signature

def count_pairs(nums, target):

Your question is Hashing Algorithm Application. Start with the requirements in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.

Problem

Constraints

0 <= nums.length <= 10^5
-10^9 <= nums[i] <= 10^9
-2 * 10^9 <= target <= 2 * 10^9
Pairs are identified by indices, so duplicate values at different indices count separately

Function Signature

def count_pairs(nums, target):

Your question is Hashing Algorithm Application. Start with the requirements in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.