PatternIQ
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14+

Core Patterns

150+

Curated Problems

4 Languages

C++, Java, Python, JS

100%

Active Recall

Pattern Architecture

The Anatomy of an Algorithmic Pattern

Deconstruct complex interview problems into intuitive mental models, clean pseudocode, and multi-language production code.

Know Your Pattern
1Mental Model & Core Intuition

Stand at opposite ends of a sorted array. Squeeze inward: sum too small → left++, sum too big → right--. Reduces O(N²) to O(N).

[1, 2, 4, 6, 8, 11]Target = 10

Step 1: 1+11=12 (Too Big → right--)

Step 2: 1+8=9 (Too Small → left++)

Step 3: 2+8=10 🎉 Match Found!

2Identification Signals

• Input: Sorted array or string (or easily sorted).

• Keywords: Two Sum II, 3Sum, Container With Most Water, Palindrome.

3Execution Recipe & Rule

left = 0, right = N - 1 → while (left < right)

Rule: If searching pairs/boundaries in sorted seq, squeeze inward from 0 and N-1.

Canonical Framework100% Deterministic
PseudocodeUniversal Logic

twoSumSorted.algo

Language-agnostic logic flow with step-by-step pointers & syntax highlighting.

two-sum-sorted.algo
1FUNCTION twoSumSorted(arr, target):
2 left = 0
3 right = LENGTH(arr) - 1
4
5 WHILE left < right:
6 currentSum = arr[left] + arr[right]
7
8 IF currentSum == target:
9 RETURN [left, right]
10 ELSE IF currentSum < target:
11 left = left + 1 // Need larger sum
12 ELSE:
13 right = right - 1 // Need smaller sum
14
15 RETURN [-1, -1]
Time: O(N)Space: O(1)Single Pass Execution
CodeMulti-Lang
two-sum-sorted.cpp
1vector<int> twoSumSorted(const vector<int>& arr, int target) {
2 int left = 0;
3 int right = arr.size() - 1;
4
5 while (left < right) {
6 int currentSum = arr[left] + arr[right];
7
8 if (currentSum == target) {
9 return {left, right};
10 } else if (currentSum < target) {
11 left++; // Need larger sum
12 } else {
13 right--; // Need smaller sum
14 }
15 }
16 return {-1, -1};
17}
14+ Templates Ready

Engineered for Long-Term Recall

Our spaced repetition engine queues active recall revisions just before memory decay occurs.

Pattern Recognition

Categorize problems into actionable frameworks. Recognize Two Pointers, Sliding Window, or Monotonic Stacks in under 30 seconds.

Spaced Repetition Engine

Scientific review intervals (1, 3, 7, 14, 30 days) automatically scheduled as you solve problems and rate difficulty.

Multi-Language Templates

Clean, battle-tested code templates in C++, Java, Python, and JavaScript with line-by-line breakdown of invariants.

Structured Algorithm Tracks

Start with linear array techniques and progress to graph traversals and dynamic programming.

6 Patterns

Two Pointers

Techniques involving two pointers iterating across linear structures to optimize time and space complexity.

5 Patterns

Sliding Window

Dynamic and fixed size windows across arrays or strings to solve subarray problems in O(N).

4 Patterns

Fast & Slow Pointers

Floyd's Cycle detection method for linked lists, cyclic arrays, and number transformations.

7 Patterns

Binary Search

Logarithmic search on sorted arrays, search spaces, and answer ranges with boundary conditions.

8 Patterns

Tree BFS & DFS

Level order traversals, recursion, pathfinding, and ancestor properties in binary trees.

12 Patterns

Dynamic Programming

0/1 Knapsack, Longest Common Subsequence, Matrix chain, and state-machine DP patterns.

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