Add py code for 821

Author: suukii

basic/array-stack-queue/02.shortest-distance-to-a-character.md

@@ -15,11 +15,11 @@ https://leetcode-cn.com/problems/shortest-distance-to-a-character/
   - [解法 3：贪心](#解法-3贪心)
     - [思路](#思路-2)
     - [复杂度分析](#复杂度分析-2)
-    - [代码 (JS/C++)](#代码-jsc-2)
+    - [代码 (JS/C++/Python)](#代码-jscpython)
   - [解法 4：窗口](#解法-4窗口)
     - [思路](#思路-3)
     - [复杂度分析](#复杂度分析-3)
-    - [代码 (JS/C++)](#代码-jsc-3)
+    - [代码 (JS/C++/Python)](#代码-jscpython-1)
 
 ## 题目描述
 
@@ -258,7 +258,7 @@ public:
 - 时间复杂度：$O(N)$，N 是 S 的长度。
 - 空间复杂度：$O(1)$。
 
-### 代码 (JS/C++)
+### 代码 (JS/C++/Python)
 
 JavaScript Code
 
@@ -347,6 +347,29 @@ public:
 };
 ```
 
+Python Code
+
+```py
+class Solution(object):
+    def shortestToChar(self, s, c):
+        """
+        :type s: str
+        :type c: str
+        :rtype: List[int]
+        """
+        n = len(s)
+        res = [0 if s[i] == c else None for i in range(n)]
+
+        for i in range(1, n):
+            if res[i] != 0 and res[i - 1] is not None:
+                res[i] = res[i - 1] + 1
+
+        for i in range(n - 2, -1, -1):
+            if res[i] is None or res[i + 1] + 1 < res[i]:
+                res[i] = res[i + 1] + 1
+        return res
+```
+
 ## 解法 4：窗口
 
 ### 思路
@@ -360,7 +383,7 @@ public:
 - 时间复杂度：$O(N)$，N 是 S 的长度。
 - 空间复杂度：$O(1)$。
 
-### 代码 (JS/C++)
+### 代码 (JS/C++/Python)
 
 JavaScript Code
 
@@ -419,4 +442,28 @@ public:
 };
 ```
 
+Python Code
+
+```py
+class Solution(object):
+    def shortestToChar(self, s, c):
+        """
+        :type s: str
+        :type c: str
+        :rtype: List[int]
+        """
+        n = len(s)
+        res = [0 for _ in range(n)]
+
+        l = 0 if s[0] == c else n
+        r = s.find(c, 1)
+
+        for i in range(n):
+            res[i] = min(abs(i - l), abs(r - i))
+            if i == r:
+                l = r
+                r = s.find(c, l + 1)
+        return res
+```
+
 更多题解可以访问：[https://github.com/suukii/91-days-algorithm](https://github.com/suukii/91-days-algorithm)