Added RC4 stream cipher algorithm

Add Splay Tree in DS

7.c :reverse of a number with overflow check added

The correct format specifier for `size_t` is `%zu`. If C89 support is needed, `%lu` along with a cast to `unsigned long` will suffice.

Also added error checking for calloc.

Cleaned up the code and used meaningful variable names

Fixed a critical flaw where `strcpy` would write the final NUL-terminator in an invalid location invoking Undefined Behavior. Allocated one extra byte to fix it.

Cleaned up the code as well in the process

Improved code Asthetics

Cleaned up, meaningful variable names

Update BubbleSort.c

+1 byte for the NUL-terminator

Format specifier for size_t, calloc check

Leetcode solutions

updated shellSort.c

updated README.md

Fixed link to TwoSum (#1)

Added solution for #5 Longest Palindromic Substring

Added #5 longest palindromic substring

Patch 2

Patch 3

Patch 4

Fixed strSize to strlen

Seperated out checkPalindrome section

Added the alternative approach suggested by @danghai

Add more solution for leetcode

also use strtok to remove trailing "\n"

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