text: class Solution:
      """
      @param A: A string
      @param B: A string
      @return: The length of longest common subsequence of A and B
      """
      def longestCommonSubsequence(self, A, B):
          # write your code here
          if not A or not B:
              return 0
              
          n, m = len(A), len(B)
          
          dp = [[0] * (m + 1) for _ in range(n + 1)]
          
          for i in range(1, n + 1):
              for j in range(1, m + 1):
                  dp[i][j] = max(dp[i - 1][j], dp[i][j - 1])
                  if A[i - 1] == B[j - 1]:
                      dp[i][j] = max(dp[i][j], dp[i - 1][j - 1] + 1)
                      
          return dp[n][m]