week 1 solution

Author: i-mprovising

contains-duplicate/i-mprovising.py

@@ -0,0 +1,12 @@
+"""
+O(n) complexity
+"""
+
+
+class Solution:
+    def containsDuplicate(self, nums: List[int]) -> bool:
+        nums_set = set(nums)
+        if len(nums) == len(nums_set):
+            return False
+        return True
+        

two-sum/i-mprovising.py

@@ -0,0 +1,13 @@
+"""
+hash table
+O(n) complexity
+"""
+
+class Solution:
+    def twoSum(self, nums: List[int], target: int) -> List[int]:
+        table = {num:idx for idx, num in enumerate(nums)}
+        for i, x in enumerate(nums):
+            y = target - x
+            if (y in table) and table[y] != i:
+                return [i, table[y]]
+

valid-anagram/i-mprovising.py

@@ -0,0 +1,16 @@
+"""
+O(n) complexity
+"""
+from collections import defaultdict
+
+class Solution:
+    def isAnagram(self, s: str, t: str) -> bool:
+        s_cnt = defaultdict(int)
+        t_cnt = defaultdict(int)
+        for char in s:
+            s_cnt[char] += 1
+        for char in t:
+            t_cnt[char] += 1
+        if s_cnt != t_cnt:
+            return False
+        return True    

valid-palindrome/i-mprovising.py

@@ -0,0 +1,16 @@
+"""
+O(n) complexity
+"""
+
+class Solution:
+    def isPalindrome(self, s: str) -> bool:
+        s = s.lower()
+        phrase = [c.lower() for c in s if c.isalpha() or c.isdigit()]
+
+        if phrase == phrase[::-1]:
+            return True
+        return False
+        
+
+
+        

valid-parentheses/i-mprovising.py

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+"""
+O(n) complexity
+"""
+class Solution:
+    def isValid(self, s: str) -> bool:
+        open_brackets = ["(", "{", "["]
+        bracket_map = {"(":")", "{":"}", "[":"]"}
+        stack = []
+        for char in s:
+            if char in open_brackets:
+                stack.append(char)
+                continue
+            if not stack: # no matching open bracket for char
+                return False
+            open_b = stack.pop() # last in open bracket
+            if bracket_map[open_b] != char: # dismatch between open b and close b
+                return False
+        if stack: # open bracket remaining
+            return False
+        return True
+            
+