1. class Solution:   # 循环写法
    2.     def longestCommonSubsequence(self, text1: str, text2: str) -> int:
    3.         m = len(text1) + 1
    4.         n = len(text2)+1
    5.         dp=[[0]*n for _ in range(m)]
    6.         for i in range(1,n): # 为什么要从1开始：因为dp[0][0]=0，从dp[1][1]开始比较
    7.             for j in range(1,m): # 计算顺序是自底向上
    8.                 if text1[i]==text2[j]:
    9.                     dp[i][j]=dp[i-1][j-1]+1
    10.                 else:
    11.                     dp[i][j] = max(dp[i][j-1],dp[i-1][j])
    12.         return  dp[m-1][n-1]