# Category: String

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.

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## 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.

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## Group anagrams together from given list of words

Given a list of words, efficiently group all anagrams together.   X and Y are anagrams if by rearranging the letters of X, we can get Y using all the original letters of X exactly once.

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## Find all possible combinations by replacing given digits with characters of the corresponding list

Given N lists of characters and a number whose digits lies between [1-N], print all possible combinations by replacing its digits with characters of the corresponding list. If any digit of the number gets repeated, it should be replaced by same character considered in its previous occurrence.

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## Isomorphic Strings

Given two strings, determine if they are isomorphic. Two strings X and Y are called isomorphic if all occurrences of each character in X can be replaced with another character to get Y and vice-versa.