Validate an IP address

Validate an IP address (IPv4). A valid IPv4 address must be in the form of XXX.XXX.XXX.XXX, where XXX is a number from 0-255.  

Run Length Encoding (RLE) data compression algorithm

Run length encoding (RLE) is a very simple form of lossless data compression which runs on sequences having same value occurring many consecutive times and it encode the sequence to store only a single value and its count.

Longest even length palidromic sum substring

Find the length of longest contiguous substring of a string, such that the length of the substring is 2*N digits and the sum of the leftmost N digits is equal to the sum of the rightmost N digits. If there is no such substring, return 0.