[jungsiroo] Week 1

contains-duplicate/jungsiroo.py

@@ -0,0 +1,18 @@
+class Solution:
+    def containsDuplicate(self, nums: List[int]) -> bool:
+        # Slow - tc : O(n) / sc : O(1)
+
+        """return len(set(nums)) != len(nums)"""
+
+        # Fast - tc : O(n) / sc : O(n)
+        check = set()
+
+        for num in nums:
+            if num in check:
+                return True
+            check.add(num)
+
+        return False
+
+
+

house-robber/jungsiroo.py

@@ -0,0 +1,39 @@
+class Solution:
+    def bfs(self, nums):
+        from collections import deque
+        queue = deque()
+
+        # price, idx, robbed prev
+        queue.append([0, 0, False])
+        queue.append([0, 0, True])
+        ret = 0
+
+        while queue:
+            price, idx, prev = queue.popleft()
+            ret = max(ret, price)
+            if idx == len(nums):
+                continue
+
+            if prev: 
+                queue.append([price, idx+1, False])
+            else:
+                queue.append([price, idx+1, False])
+                queue.append([price+nums[idx], idx+1, True])
+
+        return ret 
+
+    def rob(self, nums: List[int]) -> int:
+        # BFS - Slow and out of memory
+        """return self.bfs(nums)"""
+
+        # DP
+        n = len(nums)
+        record = [[0]*n for _ in range(2)]
+        record[1][0] = nums[0]
+
+        for i in range(1, n):
+            record[1][i] = max(record[0][i-1]+nums[i], record[1][i])
+            record[0][i] = max(record[1][i-1], record[0][i-1])
+
+        return max(record[1][-1], record[0][-1])
+

top-k-frequent-elements/jungsiroo.py

@@ -0,0 +1,26 @@
+class Solution:
+    def topKFrequent(self, nums: List[int], k: int) -> List[int]:
+        # Naive Solution
+        # TC : O(nlogn)
+        # SC : O(n)
+
+        cnt = dict()
+        for num in nums:
+            cnt[num] = cnt.get(num, 0) + 1
+
+        """
+        ret = dict(sorted(cnt.items(), key=lambda x:(-x[1], x[0])))
+        return list(ret.keys())[:k]
+        """
+
+        # Follow up Solution
+        # TC : O(nlog(k))
+        # SC : O(n)
+
+        import heapq
+
+        ret = [(-c, num) for num, c in cnt.items()]
+        heapq.heapify(ret)
+
+        return [heapq.heappop(ret)[1] for _ in range(k)]
+

valid-palindrome/jungsiroo.py

@@ -0,0 +1,7 @@
+import re
+
+class Solution:
+    def isPalindrome(self, s: str) -> bool:
+		# Fastest - tc : O(n) / sc : O(1
+        s = ''.join(re.findall(r'[a-z0-9]+', s.lower()))
+        return s == ''.join(reversed(s))