twoSum Algorithm : How to improve this?

Question

I felt like doing an algorithm and found this problem on leetcode

Given an array of integers, find two numbers such that they add up to a specific target num

Answer 1

Sort the array. Make two pointers point at first and last (x and X). Run this in a loop:

if      (a[X]+a[x] >  N) then X-- 
else if (a[X]+a[x] <  N) then x++
else if (a[X]+a[x] == N) then found.

if (x > X) then no numbers exist.

O(nlogn) time, O(1) memory