[printjin-gmailcom] Week 4 Solutions

coin-change/printjin-gmailcom.py

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+class Solution:
+    def coinChange(self, coins, amount):
+        dp = [float('inf')] * (amount + 1)
+        dp[0] = 0
+        for coin in coins:
+            for x in range(coin, amount + 1):
+                dp[x] = min(dp[x], dp[x - coin] + 1)
+        return dp[amount] if dp[amount] != float('inf') else -1

find-minimum-in-rotated-sorted-array/printjin-gmailcom.py

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+from typing import List
+
+class Solution:
+    def findMin(self, nums):
+        left, right = 0, len(nums) - 1
+        while left < right:
+            mid = (left + right) // 2
+            if nums[mid] > nums[right]:
+                left = mid + 1
+            else:
+                right = mid
+        return nums[left]

maximum-depth-of-binary-tree/printjin-gmailcom.py

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+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+
+class Solution:
+    def maxDepth(self, root: Optional[TreeNode]) -> int:
+        if not root:
+            return 0
+        return 1 + max(self.maxDepth(root.left), self.maxDepth(root.right))

merge-two-sorted-lists/printjin-gmailcom.py

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+class ListNode:
+    def __init__(self, val=0, next=None):
+        self.val = val
+        self.next = next
+
+class Solution:
+    def mergeTwoLists(self, list1, list2):
+        dummy = ListNode()
+        current = dummy
+        while list1 and list2:
+            if list1.val < list2.val:
+                current.next = list1
+                list1 = list1.next
+            else:
+                current.next = list2
+                list2 = list2.next
+            current = current.next
+        current.next = list1 if list1 else list2
+        return dummy.next

word-search/printjin-gmailcom.py

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+from typing import List
+
+class Solution:
+    def exist(self, board, word):
+        m, n = len(board), len(board[0])
+        def dfs(x, y, index):
+            if index == len(word):
+                return True
+            if x < 0 or x >= m or y < 0 or y >= n or board[x][y] != word[index]:
+                return False
+            temp = board[x][y]
+            board[x][y] = '#'
+            found = (
+                dfs(x + 1, y, index + 1) or dfs(x - 1, y, index + 1) or dfs(x, y + 1, index + 1) or dfs(x, y - 1, index + 1)
+                )
+            board[x][y] = temp
+            return found
+
+        for i in range(m):
+            for j in range(n):
+                if dfs(i, j, 0):
+                    return True
+        return False