Posted: January 2025 | Reading time: 10 minutes

The goal: Land a FAANG job (Facebook/Meta, Amazon, Apple, Netflix, Google) or any top tech company.

The barrier: The coding interview.

It's brutal. You have 45 minutes to solve an algorithmic problem. No Google. No Stack Overflow. No copy-paste.

But here's the secret: Coding interviews are learnable skills.

This is how to prepare—using CoderKit.

What Actually Happens in Coding Interviews

You sit down with an interviewer (video call).

Interviewer: "You have 45 minutes. Here's a problem. Solve it."

Example problem: "Given an array of integers, find two numbers that add to a target sum."

Input: nums = [2, 7, 11, 15], target = 9
Output: [0, 1]
Explanation: nums[0] + nums[1] = 2 + 7 = 9

What they're evaluating:

Correctness: Does your solution work?
Efficiency: Is it the best possible approach?
Communication: Can you explain your thinking?
Coding: Can you actually code? (No syntax errors, clean)
Problem-solving: Do you test edge cases?

Many candidates fail because:

Panic and freeze
Solve it but code is messy
Don't understand complexity analysis
Miss edge cases
Run out of time

The Interview Preparation Roadmap

Phase 1: Fundamentals (Weeks 1-2)

Learn:

Data Structures: Arrays, linked lists, stacks, queues, trees, graphs, heaps
Big O Complexity: Time and space complexity

Example:

# O(n) solution
def two_sum(nums, target):
    seen = {}
    for num in nums:
        complement = target - num
        if complement in seen:
            return [seen[complement], nums.index(num)]
        seen[num] = nums.index(num)
    return []

# Time: O(n), Space: O(n)
# Better than O(n²) brute force approach

Phase 2: Easy Problems (Weeks 3-4)

Solve 20-30 easy problems:

String manipulation
Array operations
Basic recursion

Example: "Reverse a string"

def reverse_string(s):
    return s[::-1]  # or
    return ''.join(reversed(s))

Phase 3: Medium Problems (Weeks 5-8)

Solve 20-30 medium problems:

Dynamic programming
Tree traversal
Graph algorithms

Example: "Longest substring without repeating characters"

def lengthOfLongestSubstring(s):
    char_index = {}
    max_len = 0
    start = 0
    
    for i, char in enumerate(s):
        if char in char_index:
            start = max(start, char_index[char] + 1)
        char_index[char] = i
        max_len = max(max_len, i - start + 1)
    
    return max_len

Phase 4: Hard Problems (Weeks 9-12)

Solve 10-20 hard problems:

Advanced DP
Complex graph problems

Phase 5: Mock Interviews (Ongoing)

Practice with:

Timer (45-60 minutes)
Real problem
Explain your thinking out loud
Code on whiteboard (limited space, like real interview)

Problem Solving Framework

When you get a problem, follow this framework:

Step 1: Clarify (2 min)

Ask questions:

What are constraints on input?
Can array be empty? Duplicates?
Can I modify input?
What should I return on error?

Example:

Interviewer: "Find two numbers that add to target" You: "Can the array be empty? Can numbers be negative? Can I use each number twice?"

Step 2: Explain Approach (3 min)

Propose solution before coding:

"I'll use a hash map. Loop through numbers, check if complement exists in map. If yes, return indices. If no, add to map."

Interviewer often corrects you here, saving wasted code.

Step 3: Code (25 min)

Write clean, readable code
Add comments
Handle edge cases
No typos

Step 4: Test (5 min)

Test with:

Simple case: [2, 7], target=9 → [0, 1]
Edge case: [], target=5 → [] (empty)
Edge case: [1], target=2 → [] (impossible)

Step 5: Optimize (5 min)

Can you do better?

Reduce time complexity?
Reduce space complexity?
Trade-offs?

Original: O(n) time, O(n) space Optimized: O(n) time, O(1) space (but only works for sorted arrays)

The Most Common Interview Topics

By frequency:

| Topic | Frequency | Examples | |---|---|---| | Arrays | 30% | Two sum, longest substring, merge intervals | | Strings | 20% | Reverse string, palindrome, regex matching | | Trees | 20% | Traverse, validate BST, lowest common ancestor | | Graphs | 15% | DFS/BFS, shortest path, topological sort | | Dynamic Programming | 15% | Fibonacci, coin change, knapsack | | Hash Maps | 10% | Two sum, anagrams, LRU cache | | Linked Lists | 10% | Reverse, cycle detection, merge lists | | Stacks/Queues | 5% | Balanced parentheses, sliding window max |

Strategy: Master the top 5 topics. That covers 85% of interviews.

Timeline: From Zero to Interview Ready

| Week | Focus | Problems | Status | |---|---|---|---| | 1-2 | Data structures + Big O | Theory + 5 easy | Fundamentals | | 3-4 | Easy problems | 20 easy | Growing confidence | | 5-6 | Medium problems | 20 medium | Getting faster | | 7-8 | Medium + patterns | 20 medium | Recognizing patterns | | 9-10 | Hard problems | 10 hard | Full depth | | 11-12 | Mock interviews | 10 timed mock | Simulation | | 13+ | Weak area review | Targeted problems | Refinement |

Total: 3 months to "ready for interviews"

How CoderKit Prepares You

1. Guided Courses

Data structures (with visualizers)
Algorithm patterns
Complexity analysis

2. Challenge Problems

Easy → Medium → Hard progression
Instant feedback
Auto-grading

3. Visualizers

See recursion execute
Watch BFS/DFS traverse
Understand sorting algorithms

4. Leaderboards

Compete globally
Benchmark your speed
Motivation to improve

5. Time Pressure

Timed challenges
Simulate interview conditions
Build speed + accuracy

Interview Tips

Tip 1: Talk Out Loud

Even if you're stuck, talk. Interviewer wants to hear your thinking.

"Okay, I'm looking at this problem... I could brute force with nested loops, but that's O(n²)... Better approach would be hash map to get O(n)... Let me think..."

Interviewer learns your thought process. They'll guide you.

Tip 2: Write Clean Code

Use meaningful variable names
Add comments
Proper indentation
No quick hacks

# Good
def two_sum(numbers, target):
    """Find two numbers that sum to target. Return indices."""
    seen = {}
    for i, num in enumerate(numbers):
        complement = target - num
        if complement in seen:
            return [seen[complement], i]
        seen[num] = i
    return []

# Bad
def ts(n, t):
    d = {}
    for i, x in enumerate(n):
        if t-x in d:
            return [d[t-x], i]
        d[x] = i

Tip 3: Handle Edge Cases

Before saying "I'm done," test:

Empty input
Single element
Duplicates
Negative numbers
Very large numbers

Tip 4: Complexity Analysis

Always state:

Time complexity
Space complexity
Why you chose this approach

Tip 5: Ask Clarifying Questions

If problem is ambiguous, ask:

"What if the array is empty?"
"Can numbers be negative?"
"What's the size of input?"

Tip 6: Practice Explaining

Record yourself solving problems. Listen back. Do you explain clearly?

Tip 7: Time Management

2 min: clarify
3 min: explain approach
25 min: code
5 min: test
10 min: optimize

If you're 30 minutes in and still coding, something's wrong. Take a step back.

The Language Question

Use the language you know best.

Most companies accept: Python, Java, C++, JavaScript

Interview language choice:

Python: Easier syntax, less bugs, slower to type
Java: Verbose, but forces precise thinking
C++: Fastest, but syntax errors likely
JavaScript: Less common, but acceptable

Recommendation: Learn in Python first. If already comfortable, use that in interviews.

Most interviewers don't care about language. They care about problem-solving.

Practice Resources

Within CoderKit:

Structured courses
Auto-graded problems
Visualizers for understanding

Outside CoderKit:

LeetCode (1900+ problems)
HackerRank (coding challenges)
InterviewBit (mock interviews)

Hybrid approach: Learn on CoderKit, practice on LeetCode.

The Salary Outcome

After interview preparation + success:

| Company | Level | Salary | Bonus | Stock | |---|---|---|---|---| | Google | L3 (new grad) | $200K | $50K | $500K (4yr) | | Meta | E3 | $220K | $60K | $600K (4yr) | | Amazon | L4 | $210K | $50K | $400K (4yr) |

Total comp: $250K-$350K/year for new grad at FAANG

Interview prep time: 3 months

ROI? About $1M+ over 4-year vesting.

That's why it matters.

Common Failure Points

1. Not Practicing Enough

Solving 20 problems isn't enough
Solve 100+
Get comfortable, not just know answers

2. Skipping Easy Problems

"I'm smart, I'll jump to hard"
Wrong. Easy problems build foundation
Do all 3 levels: easy, medium, hard

3. Not Practicing Under Pressure

Practice with timer
45-minute real conditions
Get comfortable with stress

4. Memorizing Instead of Understanding

"I saw this on LeetCode"
Interviewer asks variation, you fail
Understand why solution works

5. Not Communicating

Code silently for 45 minutes
Interviewer has no idea what you're thinking
Talk constantly, explain reasoning

Your Interview Journey

Week 1: "This is impossible" Week 4: "I'm getting easier problems" Week 8: "I'm seeing patterns" Week 12: "I'm ready"

Then:

Interview: "I got this" Next day: Offer letter 30 days later: New job, $250K+/year

It's a proven path.

What's your target company? Google? Meta? Startup? Comment below.

Start interview prep on CoderKit →

Next week: Career paths in programming. How different languages and specializations lead to different jobs and salaries.