题目：
Given two strings, find the longest common subsequence (LCS).
Your code should return the length of LCS.
Clarification
What's the definition of Longest Common Subsequence?
Example
For "ABCD" and "EDCA", the LCS is "A" (or "D", "C"), return 1.
For "ABCD" and "EACB", the LCS is "AC", return 2.
题解：
Solution 1 ()
class Solution {
public:
/**
* @param A, B: Two strings.
* @return: The length of longest common subsequence of A and B.
*/
int longestCommonSubsequence(string A, string B) {
int n1 = A.size(), n2 = B.size();
vector<vector<int>> dp(n1 + , vector<int> (n2 + , ));
for (int i = ; i <= n1; ++i) {
for (int j = ; j <= n2; ++j) {
if (A[i - ] == B[j - ]) {
dp[i][j] = dp[i - ][j - ] + ;
} else {
dp[i][j] = max(dp[i - ][j], dp[i][j - ]);
}
}
}
return dp[n1][n2];
}
};