Top 3 Easy Technical Interview Coding Questions
A curated list of beginner-friendly coding problems to build confidence in entering the world of computer science & software engineering
Getting started with technical interviews can feel like staring at a brick wall, but the trick is to master the patterns, not just the syntax. These three problems cover the fundamental data structures (Arrays, Strings, and Hash Maps) that crop up in almost every interview.
1. Two Sum
The Goal: Given an array of integers and a target, return the indices of the two numbers that add up to that target.
This is arguably the most famous coding problem because it teaches the Hash Map optimization.
def twoSum(nums, target):
prevMap = {} # val : index
for i, n in enumerate(nums):
diff = target - n
if diff in prevMap:
return [prevMap[diff], i]
prevMap[n] = i
Approach: Use a Hash Map to store values we’ve already seen. This allows us to find the “complement” (target - current) in O(1) time, making the total algorithm O(n).
2. Valid Palindrome
The Goal: Determine if a string reads the same forward and backward, ignoring non-alphanumeric characters and casing.
This problem tests string manipulation and the Two-Pointer technique, which is a vital pattern for more complex problems.
def isPalindrome(s):
# Clean the string: remove non-alphanumeric and lowercase everything
l, r = 0, len(s) - 1
while l < r:
while l < r and not s[l].isalnum():
l += 1
while r > l and not s[r].isalnum():
r -= 1
if s[l].lower() != s[r].lower():
return False
l += 1
r -= 1
return TruePro Tip: Instead of creating a reversed copy of the string (which takes extra memory), we use two pointers to meet in the middle. This keeps our space complexity at O(1).
3. FizzBuzz
The Goal: Print numbers from 1 to n. For multiples of 3, print “Fizz”; for multiples of 5, print “Buzz”; for multiples of both, print “FizzBuzz”.
This is the classic “smoke test” to ensure a candidate understands basic loops and conditionals.
def fizzBuzz(n):
result = []
for i in range(1, n + 1):
if i % 3 == 0 and i % 5 == 0:
result.append("FizzBuzz")
elif i % 3 == 0:
result.append("Fizz")
elif i % 5 == 0:
result.append("Buzz")
else:
result.append(str(i))
return result
Pro Tip: The order of the if statements matters! If you check for % 3 first, “FizzBuzz” numbers (like 15) will incorrectly stop at “Fizz.”
Where to practice these?
I highly recommend LeetCode or HackerRank. Most of these are categorized as “Easy” on those platforms.
Which of these concepts feels the most intimidating to you? The logic of the problem itself, or the time/space complexity part?
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