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49 cards

Coding Exercises Medium O(n log k)

Kth Largest Element in an Array

Push each number into a heap, trim the heap whenever it grows beyond size k, and the root will end up as the kth largest value.

Return the kth largest element from an unsorted list.

#arrays #heap #python

Coding Exercises Easy O(n * m)

Longest Common Prefix

Shrink the candidate prefix until every string starts with it. If it becomes empty, there is no shared prefix.

Return the longest common prefix shared by all strings in a list.

#python #strings

Coding Exercises Medium O(n)

Longest Consecutive Sequence

Put all numbers in a set, then expand sequences only from values whose previous number is absent. That avoids re-counting the same streak multiple times.

Return the length of the longest consecutive sequence in an unsorted array.

#arrays #python #set

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