【1143. 最长公共子序列】【python】

【1143. 最长公共子序列】【python】

Author: brucecat

动态规划系列/最长公共子序列.md

@@ -149,6 +149,7 @@ else:
 
 ======其他语言代码======
 
+### c++
 
 [Edwenc](https://github.com/Edwenc) 提供 C++ 代码：
 
@@ -183,6 +184,8 @@ public:
 };
 ```
 
+### java
+
 [Shawn](https://github.com/Shawn-Hx) 提供 Java 代码：
 
 ```java
@@ -207,4 +210,28 @@ public int longestCommonSubsequence(String text1, String text2) {
 }
 ```
 
+### python
+
+[lo-tp](http://blog.lotp.xyz/) 提供 Python 代码：
+
+```python
+class Solution(object):
+ def longestCommonSubsequence(self, text1, text2):
+ # calculate the size of the first and second string
+ sz1, sz2 = len(text1), len(text2)
+ # since to calculate dp(i,j) we only need dp(i-1,j-1), dp(i-1,j), dp(i,j-1)
+ # we don't have to save data before i-1
+ # we use dp to save dp(i-1, 0), dp(i-1, 1)....dp(i-1, sz2)
+ # we use tmp to save dp(i, 0), dp(i,1)....(dpi-1, sz2)
+ tmp, dp = [0]*(sz2+1), [0]*(sz2+1)
+ for i in range(0, sz1):
+ for j in range(0, sz2):
+ tmp[j+1] = dp[j] + \
+ 1 if text1[i] == text2[j] else max(tmp[j], dp[j+1])
+ # In the next iteration, we will calculate dp(i+1,0),dp(i+1, 1)....dp(i+1,sz2)
+ # So we exchange dp and tmp
+ tmp, dp = dp, tmp
+ return dp[-1]
+```
+