april 23

Challenges/2021/April-LeetCoding-Challenge.md

@@ -47,6 +47,7 @@ None
 |№|Title|Solution|Difficulty|
 | ----: | --- | --- | --- |
 |554.|[Brick Wall](https://leetcode.com/problems/brick-wall/)|[Python](/Medium/554.BrickWall.py)|Medium|
+|696.|[Count Binary Substrings](https://leetcode.com/problems/count-binary-substrings/)|[Python](/Easy/696.CountBinarySubstrings.py)|Easy|
 
 ## License
 The code is open-source and licensed under the [MIT License](/LICENSE).

Easy/696.CountBinarySubstrings.py

@@ -0,0 +1,56 @@
+'''
+    Give a string s, count the number of non-empty (contiguous) 
+    substrings that have the same number of 0's and 1's, 
+    and all the 0's and all the 1's in these substrings are 
+    grouped consecutively.
+
+    Substrings that occur multiple times are counted the 
+    number of times they occur.
+
+    Example:
+    Input: "00110011"
+    Output: 6
+    Explanation: There are 6 substrings that have equal number 
+                 of consecutive 1's and 0's: "0011", "01", 
+                 "1100", "10", "0011", and "01".
+
+                Notice that some of these substrings repeat 
+                and are counted the number of times they occur.
+
+                Also, "00110011" is not a valid substring 
+                because all the 0's (and 1's) are not grouped 
+                together.
+
+    Example:
+    Input: "10101"
+    Output: 4
+    Explanation: There are 4 substrings: "10", "01", "10", 
+                 "01" that have equal number of consecutive 
+                 1's and 0's.
+
+    Note:
+        - s.length will be between 1 and 50,000.
+        - s will only consist of "0" or "1" characters.
+'''
+#Difficulty: Easy
+#90 / 90 test cases passed.
+#Runtime: 300 ms
+#Memory Usage: 14.5 MB
+
+#Runtime: 300 ms, faster than 7.82% of Python3 online submissions for Count Binary Substrings.
+#Memory Usage: 14.5 MB, less than 74.34% of Python3 online submissions for Count Binary Substrings.
+
+class Solution:
+
+    def countBinarySubstrings(self, s: str) -> int:
+        count = 0
+        for i in range(len(s)-1):
+            if s[i] != s[i+1]:
+                count += self.count(s, i, i+1, s[i], s[i+1])
+        return count
+
+    def count(self, s: str, i: int, j: int, l: str, r: str) -> int:
+        while i >= 0 and j < len(s) and s[i] == l and s[j] == r:
+            i -= 1
+            j += 1
+        return (j-i)//2

README.md

@@ -1,6 +1,6 @@
 # Python solutions of LeetCode problems.
 ![Language](https://img.shields.io/badge/language-Python-blue.svg) 
-![Problems Solved](https://img.shields.io/badge/problems%20solved-545%2F1665-orange) 
+![Problems Solved](https://img.shields.io/badge/problems%20solved-546%2F1665-orange) 
 [![License](https://img.shields.io/badge/license-MIT-green.svg)](./LICENSE) 
 ![Update](https://img.shields.io/badge/update-Daily-brightgreen.svg) 
 <br><br>
@@ -22,7 +22,7 @@ In this repository provided my Python solutions of LeetCode problems.
 - [January LeetCoding Challenge](/Challenges/2021/January-LeetCoding-Challenge.md) - 27/31
 - [February LeetCoding Challenge](/Challenges/2021/February-LeetCoding-Challenge.md) - 23/28
 - [March LeetCoding Challenge](/Challenges/2021/March-LeetCoding-Challenge.md) - 23/31
-- [April LeetCoding Challenge](/Challenges/2021/April-LeetCoding-Challenge.md) - 17/30
+- [April LeetCoding Challenge](/Challenges/2021/April-LeetCoding-Challenge.md) - 18/30
 <br><br>
 ## Solutions
 *P.S. If you like this, please leave me a star.* ★
@@ -301,6 +301,7 @@ In this repository provided my Python solutions of LeetCode problems.
 |678.|[Valid Parenthesis String](https://leetcode.com/problems/valid-parenthesis-string/)|[Python](https://github.com/YuriSpiridonov/30-Day-LeetCoding-Challenge/blob/master/Week%203/ValidParenthesisString.py)|Medium|
 |682.|[Baseball Game](https://leetcode.com/problems/baseball-game/)|[Python](/Easy/682.BaseballGame.py)|Easy||
 |690.|[Employee Importance](https://leetcode.com/problems/employee-importance/)|[Python](/Easy/690.EmployeeImportance.py)|Easy|`BFS`|
+|696.|[Count Binary Substrings](https://leetcode.com/problems/count-binary-substrings/)|[Python](/Easy/696.CountBinarySubstrings.py)|Easy|
 |700.|[Search in a Binary Search Tree](https://leetcode.com/problems/search-in-a-binary-search-tree/)|[Python](/Easy/700.SearchinaBinarySearchTree.py)|Easy|`Binary Search Tree`, `Recursion`|
 |701.|[Insert into a Binary Search Tree](https://leetcode.com/problems/insert-into-a-binary-search-tree/)|[Python](/Medium/701.InsertintoaBinarySearchTree.py)|Medium|`Binary Search Tree`, `Recursion`|
 |703.|[Kth Largest Element in a Stream](https://leetcode.com/problems/kth-largest-element-in-a-stream/)|[Python](/Easy/703.KthLargestElementinaStream.py)|Easy|brute force|