Update 0115.不同的子序列.md

problems/0115.不同的子序列.md

@@ -148,7 +148,22 @@ Java：
 
 
 Python：
-
+```python
+class Solution:
+    def numDistinct(self, s: str, t: str) -> int:
+        dp = [[0] * (len(t)+1) for _ in range(len(s)+1)]
+        for i in range(len(s)):
+            dp[i][0] = 1
+        for j in range(1, len(t)):
+            dp[0][j] = 0
+        for i in range(1, len(s)+1):
+            for j in range(1, len(t)+1):
+                if s[i-1] == t[j-1]:
+                    dp[i][j] = dp[i-1][j-1] + dp[i-1][j]
+                else:
+                    dp[i][j] = dp[i-1][j]
+        return dp[-1][-1]
+```
 
 Go：