Arrays interview questions

Implement lodash xor — return the values that appear in exactly one of the given arrays, with duplicates removed.

Find the first failing version among 1..n where a monotonic isBad check flips from false to true — a boundary binary search using the fewest checks.

Move all zeroes to the end of an array in place while keeping the non-zero elements in their original order.

Implement lodash sumBy and meanBy — total and average an array by an iteratee that maps each element to a number.

Return an array where each entry is the product of every element except the one at that index, without division and in O(n).

Implement Array.prototype.myReduce — the reduce method from scratch, including the empty-array + initial-value edge cases.

Rotate an n×n matrix 90 degrees clockwise and return the result as a new array.

Decide whether an array can split into two subsets with equal sums — a subset-sum dynamic-programming problem over half the total.

Implement lodash pull and pullAll — remove every occurrence of the given values from an array in place, mutating the original.

Find the k-th smallest element of an unsorted array in average linear time by partitioning, without fully sorting it.

Implement lodash shuffle and sampleSize with an unbiased Fisher-Yates swap, taking an injectable RNG so shuffles are testable.

Find the median of two sorted arrays in logarithmic time by binary-searching for the partition that splits all the elements into equal halves.