leetcode: finished #91

content/leetcode/2023/8.md

@@ -3,6 +3,34 @@ title: "2023.8"
 draft: false
 ---
 
+# 2023.8.9
+
+```python
+#
+# @lc app=leetcode.cn id=91 lang=python3
+#
+# [91] 解码方法
+#
+
+
+# @lc code=start
+class Solution:
+    def numDecodings(self, s: str) -> int:
+        if not s:
+            return 0
+        dp = [0] * (len(s) + 1)
+        dp[0] = 1
+        for i in range(1, len(dp)):
+            if s[i - 1] != "0":
+                dp[i] += dp[i - 1]
+            if i > 1 and "10" <= s[i - 2 : i] <= "26":
+                dp[i] += dp[i - 2]
+        return dp[-1]
+
+
+# @lc code=end
+```
+
 # 2023.8.8
 
 ```python