Interview questions

4Sum

Find all unique quadruplets of distinct elements in an integer array whose values sum to a given target. Results must avoid duplicates (order irrelevant); with…

Companies: Oracle

Array · Sorting · Two Pointers

Advantage Shuffle

Given two equal-length arrays, permute nums1 to maximize the number of positions where nums1[i] > nums2[i]. This is a greedy matching problem: sort nums1 and…

Companies: Walmart Labs

Array · Greedy · Sorting · Two Pointers

Container With Most Water

Given heights of vertical lines at unit-spaced x-coordinates, pick two indices i<j to maximize the area min(height[i],height[j])*(j-i). With n up to 1e5, the problem requires…

Companies: Amazon, Bloomberg, Cisco, Flipkart +4

Array · Greedy · Two Pointers

Count Binary Substrings

Count the non-empty substrings of a binary string that contain an equal number of 0s and 1s with all 0s and all 1s each grouped…

Companies: D. E. Shaw

String · Two Pointers

Find the Index of the First Occurrence in a String

Given two strings, return the starting index of the first occurrence of needle in haystack, or -1 if absent. This is a classic substring search…

Companies: Bloomberg, Google, Meta, Microsoft

Boyer–Moore String-Search Algorithm · Knuth–Morris–Pratt Algorithm · String · String Matching

Heaters

Given positions of houses and heaters on a line, find the minimum uniform radius R such that every house is within distance R of some…

Companies: Anduril

Array · Binary Search · Sorting · Two Pointers

Linked List Cycle

Companies: Amazon, NVIDIA

Floyd's Cycle Finding Algorithm · Hash Table · Linked List · Two Pointers

Partition Array Into Two Arrays to Minimize Sum Difference

Partition the 2n integers into two equal-sized groups (choose n elements for one group) to minimize the absolute difference of their sums — a constrained…

Companies: Salesforce

Array · Binary Search · Bit Manipulation · Bitmask

Push Dominoes

Given a line of dominoes where some are initially pushed left (L), right (R), or upright (.), compute the final positions after simultaneous propagation of…

Companies: Anduril

Dynamic Programming · String · Two Pointers

Reverse String

Reverse the input array of characters in-place (O(1) extra space) so the characters appear in reverse order; array length can be up to 10^5.

Companies: Meta

String · Two Pointers

Valid Triangle Number

Count the number of triplets (i, j, k) from nums that can form triangle side lengths — i.e., three values a ≤ b ≤ c…

Companies: Bloomberg

Array · Binary Search · Greedy · Sorting