SDE - Intern

You are given ‘N’ binary tree nodes numbered from 0 to N - 1 where node ‘i’ has two children LEFT_CHILD[i] and RIGHT_CODE[i]. Return ‘True’ if and only if all the given nodes form exactly one valid binary tree. If node ‘i’ has no left child then 'LEFT_CHILD[i]' will equal -1, similarly for the right child.

Example:

Let’s say we have n=4 nodes, 'LEFT_CHILD' = {1, -1, 3, -1} and 
RIGHT_CHILD = {2, -1, -1, -1}. So the resulting tree will look like this:

It will return True as there is only one valid binary tree and each node has only one parent and there is only one root.

You have been given a string ‘A’ consisting of lower case English letters. Your task is to find the length of the longest palindromic subsequence in ‘A’.

A subsequence is a sequence generated from a string after deleting some or no characters of the string without changing the order of the remaining string characters. (i.e. “ace” is a subsequence of “abcde” while “aec” is not).

A string is said to be palindrome if the reverse of the string is the same as the actual string. For example, “abba” is a palindrome, but “abbc” is not a palindrome.

There are 5 lanes on a racetrack. One needs to find out the 3 fastest horses among total of 25. Find out the minimum number of races to be conducted in order to determine the fastest three.

Two trains, separated by a distance of 80 km, are running towards each other on the same track at a speed of 40 km/h. A bird takes flight from train X and flies towards train Y at a constant speed of 100 km/h. Once it reaches train Y, it turns and starts flying back toward train X. The bird keeps flying back and forth until both trains collide. Determine the distance traveled by the bird.