Merge branch 'week1'

Author: MJ Kang

house-robber/mandoolala.py

@@ -0,0 +1,25 @@
+from typing import List
+
+class Solution:
+    def rob(self, nums: List[int]) -> int:
+        '''
+        [Complexity]
+        Time: O(n)
+        Space: O(n)
+        '''
+        cnt = len(nums)
+
+        if cnt == 1:
+            return nums[0]
+        if cnt == 2:
+            return max(nums[0], nums[1])
+
+        dp = [0] * cnt
+        dp[0] = nums[0]
+        dp[1] = max(nums[0], nums[1])
+
+        for i in range(2, cnt):
+            # skip: dp[i-1]
+            # rob: dp[i-2]+nums[i]
+            dp[i] = max(dp[i - 1], dp[i - 2] + nums[i])
+        return max(dp)

longest-consecutive-sequence/mandoolala.py

@@ -0,0 +1,14 @@
+from typing import List
+
+class Solution:
+    def longestConsecutive(self, nums: List[int]) -> int:
+        num_set = set(nums)
+        longest = 0
+        for num in num_set:
+            if num - 1 in num_set:
+                continue
+            length = 1
+            while num + length in num_set:
+                length += 1
+            longest = max(length, longest)
+        return longest

top-k-frequent-elements/mandoolala.py

@@ -3,6 +3,29 @@
 
 class Solution:
     def topKFrequent(self, nums: List[int], k: int) -> List[int]:
+        '''
+        Using (min)heap
+        [Complexity]
+        Time: O(log n)
+        Space: O(n+k)
+        '''
+        from heapq import heappush, heappop
+        counter = {}
+        for num in nums:
+            counter[num] = counter.get(num, 0) + 1
+        heap = []
+        for num, freq in counter.items():
+            heappush(heap, (freq, num))
+            if len(heap) > k:
+                heappop(heap)
+        return [num for _, num in heap]
+        '''
+        Using hash table 
+        [Complexity]
+        Time: O(n log n)
+        Space: O(n)
+        '''
+        '''
         countDict = {}
         for num in nums:
             if num in countDict:
@@ -14,3 +37,4 @@ def topKFrequent(self, nums: List[int], k: int) -> List[int]:
         for i in range(k):
             freqElements.append(sortedDictList[i][0])
         return freqElements
+        '''