Longest Common Subsequence
Problem
Given two strings, find the longest common subsequence (LCS).
Your code should return the length of LCS.
Example
For "ABCD" and "EDCA", the LCS is "A" (or "D", "C"), return 1.
For "ABCD" and "EACB", the LCS is "AC", return 2.
Clarification
What's the definition of Longest Common Subsequence?