Algorithms

Answers of an algorithm test I've taken in the past.

Questions:

1. Write an efficient algorithm to check if a string is a palindrome. A string is a palindrome if the string matches the reverse of string. Example: 1221 is a palindrome but not 1121.

2. Write an efficient algorithm to find K-complementary pairs in a given array of integers. Given Array A, pair (i, j) is K- complementary if K = A[i] + A[j];

3. Given a large file that does not fit in memory (say 10GB), find the top 100000 most frequent phrases. The file has 50 phrases per line separated by a pipe (|). Assume that the phrases do not contain pipe. Example line may look like: Foobar Candy | Olympics 2012 | PGA | CNET | Microsoft Bing …. The above line has 5 phrases in visible region.