## 题目

Given two strings `text1`

and `text2`

, return the length of their longest common subsequence.

A subsequence of a string is a new string generated from the original string with some characters(can be none) deleted without changing the relative order of the remaining characters. (eg, “ace” is a subsequence of “abcde” while “aec” is not). A common subsequence of two strings is a subsequence that is common to both strings.

If there is no common subsequence, return 0.

Example 1:

1 | Input: text1 = "abcde", text2 = "ace" |

Example 2:

1 | Input: text1 = "abc", text2 = "abc" |

Example 3:

1 | Input: text1 = "abc", text2 = "def" |

Constraints:

`1 <= text1.length <= 1000`

`1 <= text2.length <= 1000`

- The input strings consist of lowercase English characters only.

## 思路

DP.

DP[i][j] represents the longest common subsequence of text1[0 … i] & text2[0 … j].`if text1[i] == text2[j]: DP[i][j] = DP[i - 1][j - 1] + 1`

`else: DP[i][j] = max(DP[i - 1][j], DP[i][j - 1])`

## 代码

1 | class Solution(object): |