Final exam — Binary
Three unseen problems (not covered in the lessons) to test whether you leave this section able to solve any problem of the topic: one easy, one medium and one hard. Some test cases are hidden — like the real LeetCode. Solve in Python or JavaScript.
Single Number
In an array nums, every element appears twice, except one, which appears once. Find that single one. Try to do it in O(n) time and O(1) extra space.
Example: nums = [4, 1, 2, 1, 2] → 4.
Find First and Last Position of Element in Sorted Array
Given a sorted array nums (with duplicates) and a target, return [first, last] index where target appears, or [-1, -1] if it doesn't exist. O(log n) is expected.
Example: nums = [5,7,7,8,8,10], target = 8 → [3, 4].
Koko Eating Bananas
Koko has piles of bananas (piles[i]) and h hours. At a speed k (bananas/hour), each hour she picks a pile and eats up to k of it (if the pile has fewer, she eats it all and rests for the rest of the hour). Return the smallest k that lets her eat all the bananas in h hours.
Example: piles = [3, 6, 7, 11], h = 8 → 4.