Update 0028.实现strStr.md

problems/0028.实现strStr.md

@@ -692,23 +692,38 @@ class Solution {
 ```
 
 Python3：
+（版本一）前缀表（不减一）
+
 ```python
-//暴力解法：
-class Solution(object):
-    def strStr(self, haystack, needle):
-        """
-        :type haystack: str
-        :type needle: str
-        :rtype: int
-        """
-        m, n = len(haystack), len(needle)
-        for i in range(m):
-            if haystack[i:i+n] == needle:
-                return i
+class Solution:
+    def strStr(self, haystack: str, needle: str) -> int:
+        if len(needle) == 0:
+            return 0
+        next = self.getNext(needle)
+        j = 0
+        for i in range(len(haystack)):
+            while j >= 1 and haystack[i] != needle[j]:
+                j = next[j-1]
+            if haystack[i] == needle[j]:
+                j += 1
+            if j == len(needle):
+                return i - len(needle) + 1
         return -1
+    
+    def getNext(self, needle):
+        next = [0] * len(needle)
+        j = 0
+        next[0] = j
+        for i in range(1, len(needle)):
+            while j >= 1 and needle[i] != needle[j]:
+                j = next[j-1]
+            if needle[i] == needle[j]:
+                j += 1
+            next[i] = j
+        return next
 ```
+（版本二）前缀表（减一）
 ```python
-// 方法一
 class Solution:
     def strStr(self, haystack: str, needle: str) -> int:
         a = len(needle)
@@ -739,8 +754,11 @@ class Solution:
         return next
 ```
 
+
+（版本三）前缀表（减一）
+
+
 ```python
-// 方法二
 class Solution:
     def strStr(self, haystack: str, needle: str) -> int:
         a = len(needle)
@@ -774,35 +792,36 @@ class Solution:
         return next
 ```
 
+（版本四）暴力法
+```python
+class Solution(object):
+    def strStr(self, haystack, needle):
+        """
+        :type haystack: str
+        :type needle: str
+        :rtype: int
+        """
+        m, n = len(haystack), len(needle)
+        for i in range(m):
+            if haystack[i:i+n] == needle:
+                return i
+        return -1    
+```
+（版本五）使用 index
 ```python
-// 前缀表（不减一）Python实现
 class Solution:
     def strStr(self, haystack: str, needle: str) -> int:
-        if len(needle) == 0:
-            return 0
-        next = self.getNext(needle)
-        j = 0
-        for i in range(len(haystack)):
-            while j >= 1 and haystack[i] != needle[j]:
-                j = next[j-1]
-            if haystack[i] == needle[j]:
-                j += 1
-            if j == len(needle):
-                return i - len(needle) + 1
+        try:
+            return haystack.index(needle)
+        except ValueError:
             return -1
-    
-    def getNext(self, needle):
-        next = [0] * len(needle)
-        j = 0
-        next[0] = j
-        for i in range(1, len(needle)):
-            while j >= 1 and needle[i] != needle[j]:
-                j = next[j-1]
-            if needle[i] == needle[j]:
-                j += 1
-            next[i] = j
-        return next
 ```
+（版本六）使用 find
+```python
+class Solution:
+    def strStr(self, haystack: str, needle: str) -> int:
+        return haystack.find(needle)
+       
 
 Go：