Quick recall mode

Keywords first, details second.

Use this mode when you want memory triggers only: title, summary, tags, and bullet anchors without long answers getting in the way.

Results update as you type. Press / to jump straight into search.

Type Category Tag Difficulty Keywords only

Quick recall

374 cards

Coding Exercises Medium O(n)

Longest Substring Without Repeating Characters

Expand the right edge one character at a time and move the left edge forward whenever a duplicate falls inside the current window. Track the maximum window length as you go.

Find the length of the longest substring that contains no repeated characters.

#python #sliding-window #strings

Coding Exercises Medium O(1)

LRU Cache

Store items in an OrderedDict, move keys to the end whenever they are read or updated, and evict the oldest item when capacity is exceeded.

Implement an LRU cache with O(1) get and put operations.

#cache #design #hash-map #python

Coding Exercises Easy O(n)

Majority Element

Track a running candidate and increment or decrement a counter as you scan. When the counter drops to zero, start fresh with the current value as the new candidate.

Return the element that appears more than n // 2 times in an array.

#arrays #greedy #python

Coding Exercises Medium O(n)

Maximum Subarray

Track the best subarray ending at the current position and reset only when starting fresh is better than extending the previous run.

Return the largest possible sum of a contiguous subarray.

#arrays #dynamic-programming #python

Coding Exercises Medium O(n log n)

Merge Intervals

Sort intervals by start, then compare each interval with the current merged tail. Extend the tail end when ranges overlap; otherwise append a new interval.

Merge all overlapping intervals and return the condensed list.

#intervals #python #sorting

Coding Exercises Easy O(n + m)

Merge Two Sorted Arrays

Walk both arrays with two pointers, append the smaller value each step, and then append the remaining tail from whichever array is not exhausted yet.

Merge two sorted arrays into one sorted list.

#arrays #python #two-pointers

Coding Exercises Easy O(n + m)

Merge Two Sorted Linked Lists

Use a dummy head and repeatedly attach the smaller current node from either list. When one list runs out, append the remaining nodes from the other list.

Merge two sorted linked lists and return the head of the merged list.

#linked-list #python #two-pointers

Coding Exercises Medium O(1)

Push each value onto the main stack and also onto a min stack whenever it is less than or equal to the current minimum. When popping, remove it from the min stack too if it matches the current minimum.

Implement a stack that supports push, pop, top, and get_min in constant time.

#design #python #stack

Coding Exercises Hard O(n + m)

Minimum Window Substring

Track how many required characters are satisfied as you grow the right edge. Once the window is valid, shrink from the left to find the smallest valid window before expanding again.

Return the smallest substring of s that contains all characters from t.

#hash-map #python #sliding-window #strings

Coding Exercises Easy O(n)

Missing Number

Compute the expected sum from 0 through n and subtract the actual sum of the list to find the missing number.

Given numbers from 0 to n with one missing, return the missing value.

#arrays #math #python

Coding Exercises Easy O(n)

Move Zeroes

Scan once, swap each non-zero value into the next write position, and advance that write pointer.

Move all zeroes to the end of the list while keeping the relative order of non-zero values.

#arrays #python #two-pointers

Coding Exercises Medium O(n)

Next Greater Element

Walk the array from right to left and maintain a stack of candidates greater than the current value. Pop smaller values because they can never be the next greater element for earlier entries.

For each element in an array, return the next greater element to its right, or -1 if none exists.

#arrays #python #stack