Crack the loop, not just the problem.

Java, SQL and OOP interview questions with clear answers, plus pattern-based DSA. Full solutions, clear reasoning, written for people who want the offer.

# Pattern: two pointers on a sorted array
def pair_sum(nums, target):
    lo, hi = 0, len(nums) - 1
    while lo < hi:
        s = nums[lo] + nums[hi]
        if s == target:
            return lo, hi
        if s < target: lo += 1
        else: hi -= 1
    return None   # O(n) time, O(1) space