[doh6077] WEEK 07 solutions

reverse-linked-list/doh6077.py

@@ -0,0 +1,19 @@
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+# 206. Reverse Linked List
+# 1. Use two pointers 
+# 2. one pointer indicates the current node and another pointer indicate the previous node 
+class Solution:
+    def reverseList(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        curr = head
+        prev = None
+
+        while curr is not None:
+            nextNode = curr.next
+            curr.next = prev
+            prev = curr 
+            curr = nextNode 
+        return prev

set-matrix-zeroes/doh6077.py

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+
+# 73. Set Matrix Zeroes
+class Solution:
+    def setZeroes(self, matrix: list[list[int]]) -> None:
+        """
+        Do not return anything, modify matrix in-place instead.
+        """
+        zeroIndex = []
+        # Brute Force
+        # 1. first find which columns have zero
+        # 2. set the entire row to zero
+        for subIndex, sublist in enumerate(matrix):
+            for elementIndex, element in enumerate(sublist):
+                print(f"Checking element at row {subIndex}, column {elementIndex}: {element}"   )
+                if element == 0:
+                    zeroIndex.append(elementIndex)  
+                    sublist = [0] * len(sublist)
+                    matrix[subIndex] = sublist
+        for subIndex, sublist in enumerate(matrix):
+            for elementIndex, element in enumerate(sublist):
+                if elementIndex in zeroIndex:
+                    sublist[elementIndex] = 0           
+        print(zeroIndex)    
+
+sol = Solution()
+matrix = [[1,1,1],[1,0,1],[1,1,1]]
+sol.setZeroes(matrix)
+print(matrix)  # Output should be [[1,0,1],[0,0,0],[1,0,1]]