JavaScript Interview Programs

Return whether the string reads identically in both directions; comparison is case-sensitive and includes spaces.

Easy· Strings ·10 min

Return whether n is prime; integers below 2 are not prime.

Easy· Numbers ·10 min

Return whether two ASCII strings contain the same characters with the same multiplicities; case and spaces matter.

Easy· Strings ·10 min

Compute n factorial, with 0 factorial defined as 1.

Easy· Numbers ·10 min

Return the index of target in a strictly increasing integer array, or -1 if it is absent.

Easy· Sorting & Searching ·10 min

Return the first character appearing exactly once, or the empty string if none exists.

Easy· Strings ·10 min

Return the second-largest distinct integer, or null when fewer than two distinct values exist.

Easy· Arrays ·10 min

Return the first n Fibonacci numbers starting with 0, 1.

Easy· Numbers ·10 min

Remove duplicate integers, preserving the order of their first appearance.

Easy· Arrays ·10 min

Move all zeroes after the nonzero values while retaining the relative order of nonzero values.

Easy· Arrays ·10 min

Reverse every character of the supplied ASCII string.

Easy· Strings ·10 min

Split an integer array into consecutive chunks of size k; the final chunk may be shorter.

Easy· Arrays ·10 min

Replace each maximal run with its character followed by its decimal count, including counts of one. Input contains only lowercase English letters.

Medium· Strings ·20 min

Count objects by their string-valued property named key. Return [value,count] pairs ordered by the first occurrence of each value; treat property names literally, including __proto__.

Medium· Collections ·20 min

Return the longest prefix shared by all input strings; return an empty string for an empty list.

Medium· Strings ·20 min

Return the maximum length of a contiguous substring containing no repeated ASCII character.

Medium· Strings ·20 min

Return the largest sum of a nonempty contiguous subarray; return null for an empty array.

Medium· Arrays ·20 min

Return indices [i,j] with i < j whose values sum to target, or [] if none exist. Choose the smallest possible j, then the smallest i.

Medium· Hashing ·20 min

Flatten a nested array of JSON primitive values into one array in left-to-right order. Preserve null, booleans, strings and numbers as values.

Medium· Recursion ·20 min

Return distinct values present in both arrays, ordered by their first occurrence in the first array.

Medium· Hashing ·20 min

Merge closed integer intervals whenever they overlap or touch at an endpoint. Return disjoint intervals ordered by their starts; adjacent intervals such as [1,2] and [3,4] do not overlap.

Medium· Sorting & Searching ·20 min

Merge two nondecreasing integer arrays into one nondecreasing array, retaining duplicates.

Medium· Two Pointers ·20 min

Rotate an integer array right by k positions; k may exceed the array length.

Medium· Arrays ·20 min

Return matrix values in clockwise spiral order, starting at the top-left corner. An empty matrix returns [].

Medium· Matrices ·20 min

Return whether a string of brackets (), [] and {} is correctly nested and balanced.

Medium· Strings ·20 min

Return whether two JSON values are deeply equal. Object key order is irrelevant, array order matters, and primitive values must have the same type and value.

Hard· Recursion ·35 min

Return the minimum number of single-character insertions, deletions and substitutions needed to transform the first string into the second. Each operation costs one.

Hard· Dynamic Programming ·35 min

Treat the array as unit-width nonnegative bar heights and return the total amount of rain water trapped between bars.

Hard· Two Pointers ·35 min

Return the maximum value of each consecutive window of k integers.

Hard· Stack & Queue ·35 min

Return the shortest substring of source containing all characters of target with their required multiplicities. Break ties by earliest start; return an empty string if target is empty or no window exists.

Hard· Sliding Window ·35 min