Interview Q&A / Data Structures & Algorithms

1. How do you merge two sorted arrays into one sorted array?

   Use two pointers, one at the start of each array. Compare the two current elements, copy the smaller one to the result and move that pointer forward. When one array runs out, copy the rest of the other. This is O(n + m) time, much better than joining and sorting again.

   BeginnerIn-depthCoding3 min read
2. How do you implement merge sort in JavaScript?

   Recursively split the array into two halves until single elements remain, then merge the sorted halves by repeatedly taking the smaller front element. It runs in O(n log n) time with O(n) extra space.

   BeginnerQuick answerCoding1 min read
3. Why does [10, 9, 1].sort() return [1, 10, 9] in JavaScript?

   By default sort converts elements to strings and compares them in dictionary order, so "10" comes before "9". Pass a comparator such as (a, b) => a - b to sort numbers numerically.

   BeginnerQuick answerCoding1 min read