[8804who] WEEK 09 Solutions

linked-list-cycle/8804who.py

@@ -0,0 +1,19 @@
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+
+class Solution:
+    def hasCycle(self, head: Optional[ListNode]) -> bool:
+        fast = head
+        slow = head
+        while fast and fast.next:
+            fast = fast.next.next
+            slow = slow.next
+
+            if fast == slow:
+                return True
+
+        return False
+

maximum-product-subarray/8804who.py

@@ -0,0 +1,21 @@
+class Solution:
+    def maxProduct(self, nums: List[int]) -> int:
+        answer = max(nums)
+
+        cumprod = 1
+        cumprod_to_first_neg = 1
+
+        for num in nums:
+            if num == 0:
+                cumprod = 1
+                cumprod_to_first_neg = 1
+            else:
+                cumprod *= num
+                if cumprod > 0:
+                    answer = max(answer, cumprod)
+                else:
+                    answer = max(answer, cumprod//cumprod_to_first_neg)
+                if cumprod_to_first_neg > 0:
+                    cumprod_to_first_neg *= num
+        return answer
+

minimum-window-substring/8804who.py

@@ -0,0 +1,34 @@
+from collections import Counter, defaultdict
+class Solution:
+    def minWindow(self, s: str, t: str) -> str:
+        answer = ''
+        counter = Counter(t)
+        now = defaultdict()
+
+        start = 0
+        end = 0
+
+        now[s[start]] = 1
+
+        while start<=end and end < len(s):
+            enough = True
+            for key in counter.keys():
+                if key not in now or now[key] < counter[key]:
+                    enough = False
+
+            if enough:
+                if answer == '' or len(answer) > end-start+1:
+                    answer = s[start:end+1]
+
+                now[s[start]] -= 1
+                start += 1
+            else:
+                end += 1
+                if end == len(s):
+                    break
+                if s[end] not in now:
+                    now[s[end]] = 0
+                now[s[end]] += 1
+
+        return answer
+

pacific-atlantic-water-flow/8804who.py

@@ -0,0 +1,58 @@
+from collections import deque
+
+class Solution:
+    def pacificAtlantic(self, heights: List[List[int]]) -> List[List[int]]:
+        answer = []
+        h, w = len(heights), len(heights[0])
+        moves = [[-1, 0], [1, 0], [0, -1], [0, 1]]
+
+        visited1 = [[False for _ in range(w)] for _ in range(h)]
+        visited2 = [[False for _ in range(w)] for _ in range(h)]
+
+        q1 = deque()
+        q2 = deque()
+
+        for i in range(w):    
+            q1.append((0, i))
+            q2.append((h-1, i))
+            visited1[0][i] = True
+            visited2[h-1][i] = True
+
+        for i in range(h):
+            q1.append((i, 0))
+            q2.append((i, w-1))
+            visited1[i][0] = True
+            visited2[i][w-1] = True
+
+        while q1:
+            y, x = q1.popleft()
+
+            for move in moves:
+                next_y, next_x = y+move[0], x+move[1]
+
+                if 0 <= next_y < h and 0 <= next_x < w:
+                    if visited1[next_y][next_x]:
+                        continue
+                    if heights[next_y][next_x] >= heights[y][x]:
+                        visited1[next_y][next_x] = True
+                        q1.append((next_y, next_x))
+
+        while q2:
+            y, x = q2.popleft()
+
+            for move in moves:
+                next_y, next_x = y+move[0], x+move[1]
+
+                if 0 <= next_y < h and 0 <= next_x < w:
+                    if visited2[next_y][next_x]:
+                        continue
+                    if heights[next_y][next_x] >= heights[y][x]:
+                        visited2[next_y][next_x] = True
+                        q2.append((next_y, next_x))
+
+        for i in range(h):
+            for j in range(w):
+                if visited1[i][j] and visited2[i][j]:
+                    answer.append([i, j])
+        return answer
+

sum-of-two-integers/8804who.py

@@ -0,0 +1,5 @@
+import math
+class Solution:
+    def getSum(self, a: int, b: int) -> int:
+        return int(math.log(2**a * 2**b, 2))
+