Last-minute revision, formula sheets, and code templates — all in one place.
Two pointers, sliding window, prefix sums — all patterns with time complexity.
Insert, delete, reverse, detect cycle — with visual diagrams and code templates.
Inorder, preorder, postorder, BFS — recursive and iterative code in Python and C++.
How to identify DP problems + 8 core patterns with examples and state transitions.
Linear regression, gradient descent, loss functions, regularization — all key formulas.
CSS flexbox, grid, common JS patterns, fetch API — all on one printable sheet.
Copy-paste these templates into your editor during practice.
# Standard binary search def binary_search(arr, target): left, right = 0, len(arr) - 1 while left <= right: mid = left + (right - left) // 2 if arr[mid] == target: return mid elif arr[mid] < target: left = mid + 1 else: right = mid - 1 return -1
# Variable size sliding window def sliding_window(arr): left = 0 result = 0 window = {} # or a running sum for right in range(len(arr)): # Expand window window[arr[right]] = window.get(arr[right], 0) + 1 # Shrink window (condition) while invalid(window): window[arr[left]] -= 1 left += 1 result = max(result, right - left + 1) return result
from collections import deque def bfs(graph, start): visited = {start} queue = deque([start]) while queue: node = queue.popleft() process(node) # do something for neighbor in graph[node]: if neighbor not in visited: visited.add(neighbor) queue.append(neighbor)
# Bottom-up DP (Climbing Stairs) def climb_stairs(n): if n <= 2: return n prev2, prev1 = 1, 2 for i in range(3, n + 1): curr = prev1 + prev2 prev2 = prev1 prev1 = curr return prev1 # O(n) time, O(1) space ✅