Why Most Coding Interview Prep Fails
The most common approach graduates take is to grind hundreds of LeetCode problems in a random order, burning out before they've covered the patterns that actually come up. The result: they've seen 200 problems but can't reliably solve a new one under pressure.
Effective preparation is structured, deliberate, and company-specific. This guide gives you a 30-day plan that covers the right material in the right order - with a focus on the patterns and question types most common at UK graduate tech interviews.
If you want to understand the broader hiring context before diving in, start with our guide: how to get a graduate job in tech.
What UK Graduate Coding Interviews Actually Test
Understanding the testing format for your target companies is the first step. UK graduate tech interviews typically fall into one of three formats:
- Online coding assessment (OCA) - automated platform (HackerRank, Codility, CoderPad). Timed. 1–3 problems in 60–90 minutes. Tested blind, no feedback in real time.
- Live technical screen - video call with an engineer. You share your screen and code in a shared editor (CoderPad, Google Docs). They observe your process and ask questions.
- On-site / virtual final round - 1–4 technical interviews in one session. May include system design, behavioural, and coding rounds.
Each format requires slightly different preparation. OCAs test pure problem-solving speed. Live screens test communication, process, and the ability to handle hints. Final rounds test depth.
The Core Patterns You Must Know
Master these 8 patterns and you'll be able to approach any problem you encounter:
- Hashmaps and sets - frequency counting, existence checking, O(1) lookups
- Two pointers - sorted arrays, palindromes, pair sums
- Sliding window - subarray/substring problems, max/min in a range
- Binary search - sorted arrays, and "minimum/maximum satisfying a condition" problems
- BFS and queues - shortest path, level-order traversal, graph connectivity
- DFS and recursion - tree traversal, permutations, combinations
- Dynamic programming - optimisation, counting paths, minimum cost
- Greedy algorithms - interval scheduling, minimum spanning trees, locally optimal choices
For a deeper breakdown of how these patterns appear in UK-specific interviews, see our guide: LeetCode patterns for UK tech interviews.
The 30-Day Preparation Plan
Week 1 - Foundation (Days 1–7)
Focus: Hashmaps, arrays, strings, two pointers
Daily routine: 1 Easy + 1 Medium problem. Focus on understanding and articulation, not speed.
Essential problems: Two Sum (LC1), Valid Anagram (LC242), Longest Substring Without Repeating Characters (LC3), Best Time to Buy and Sell Stock (LC121), 3Sum (LC15).
Key habit to build: Before coding, always spend 3–5 minutes talking through your approach - as if explaining to the interviewer. This is the skill that separates good candidates from great ones in live interviews.
Week 2 - Trees and Graphs (Days 8–14)
Focus: Binary trees, BFS, DFS, linked lists
Essential problems: Binary Tree Level Order Traversal (LC102), Maximum Depth of Binary Tree (LC104), Number of Islands (LC200), Merge Two Sorted Lists (LC21), Reverse Linked List (LC206).
Key insight: Tree problems are extremely common in UK graduate interviews. A huge percentage of tree problems reduce to "run DFS and track some state." Practice recognising this pattern.
Week 3 - Dynamic Programming and Binary Search (Days 15–21)
Focus: 1D DP, 2D DP, binary search on answer
Essential problems: Climbing Stairs (LC70), Coin Change (LC322), Longest Common Subsequence (LC1143), Koko Eating Bananas (LC875), Jump Game (LC55).
Key habit: For DP problems, always define your state clearly before writing any code. "dp[i] represents..." - this one habit prevents most DP errors.
Week 4 - Mock Interviews and Company-Specific Prep (Days 22–30)
Focus: Simulated interview conditions, target-company preparation
Daily routine: One timed mock interview (45 minutes, 1–2 problems). Use Pramp, interviewing.io, or a study partner.
Company prep: For each company you're interviewing at, use GradSignal's interview playbooks to review the specific questions, patterns, and behavioural questions they use. Tailor your final week to the companies on your calendar.
How to Perform on the Day
Technical knowledge only matters if you can access it under pressure. These habits make a measurable difference in live interviews:
- Ask clarifying questions first. "Can the input array be empty? Can values be negative?" This signals engineering maturity and prevents solving the wrong problem.
- State your approach before coding. "My plan is to use a sliding window here because..." Getting buy-in before you code means the interviewer can redirect you if you're going wrong - before you've wasted 10 minutes.
- Start with brute force. Always mention the naive solution and its complexity before optimising. It demonstrates you understand the problem space.
- Think out loud throughout. Silence is the enemy in live coding interviews. Narrate your reasoning even when you're stuck - "I know this can't be the optimal approach because of the nested loop here..."
- Test your code with an example. Before saying you're done, trace through your code manually with a simple input. Interviewers respond very well to candidates who catch their own bugs.
Your 30-Day Plan - Download and Print
Ready to start your structured prep? Create a free GradSignal account to access your personalised preparation tracker, set job alerts for roles you're targeting, and use company-specific interview playbooks to know exactly what to prepare for each employer.
The graduates who land the best tech roles don't prep harder - they prep smarter. Build the right habits in week one and the rest follows.