Array element products except self

Author: ratulb

codes/product_of_array_except_self.mojo

@@ -0,0 +1,40 @@
+# Function to compute the product of all elements in the list except the one at each index
+fn product_except_self(nums: List[Int]) -> List[Int]:
+    # If the input list is empty, return it as is
+    if len(nums) == 0:
+        return nums
+
+    # Store the length of the input list
+    len = len(nums)
+
+    # Initialize the result list with all 1s. This will store our final answer.
+    result = List(1) * len
+
+    # prefix_product holds the product of all elements to the *left* of the current index
+    prefix_product = 1
+    for idx in range(len):
+        # For each index, store the current prefix product
+        result[idx] = prefix_product
+        # Update the prefix product by multiplying it with the current number
+        prefix_product *= nums[idx]
+
+    # suffix_product holds the product of all elements to the *right* of the current index
+    suffix_product = 1
+    # Iterate from right to left
+    for idx in range(len - 1, -1, -1):
+        # Multiply the result at index with the current suffix product
+        result[idx] *= suffix_product
+        # Update the suffix product by multiplying with current number
+        suffix_product *= nums[idx]
+
+    return result
+
+
+# Entry point
+fn main():
+    # Example input
+    nums = List(1, 2, 3, 4)
+    # Call the function to get result
+    result = product_except_self(nums)  # Output should be [24, 12, 8, 6]
+    # Print the result
+    print(result.__str__())

docs/index.md

@@ -5,3 +5,4 @@
 - [ Buy and Sell Stock 1](buy_and_sell_stock.md) ➔ Maximize profit by buying once and selling later on a future day.
 - [ Buy and Sell Stock 2](buy_and_sell_stock_2.md) ➔ Maximize profit by buying and selling multiple times.
 - [ Longest Substring Without Repeating Characters](longest_substr_no_char_repeats.md) ➔ Given a string s, find the length of the longest substring without duplicate characters.
+- [ Product of Array Except Self](product_of_array_except_self.md) ➔ Return an array where each element is the product of all others in the input array.

docs/product_of_array_except_self.md

@@ -0,0 +1,43 @@
+### Function to compute the product of all elements in the list except the one at each index
+
+```python
+fn product_except_self(nums: List[Int]) -> List[Int]:
+    # If the input list is empty, return it as is
+    if len(nums) == 0:
+        return nums
+
+    # Store the length of the input list
+    len = len(nums)
+
+    # Initialize the result list with all 1s. This will store our final answer.
+    result = List(1) * len
+
+    # prefix_product holds the product of all elements to the *left* of the current index
+    prefix_product = 1
+    for idx in range(len):
+        # For each index, store the current prefix product
+        result[idx] = prefix_product
+        # Update the prefix product by multiplying it with the current number
+        prefix_product *= nums[idx]
+
+    # suffix_product holds the product of all elements to the *right* of the current index
+    suffix_product = 1
+    # Iterate from right to left
+    for idx in range(len - 1, -1, -1):
+        # Multiply the result at index with the current suffix product
+        result[idx] *= suffix_product
+        # Update the suffix product by multiplying with current number
+        suffix_product *= nums[idx]
+
+    return result
+
+
+# Entry point
+fn main():
+    # Example input
+    nums = List(1, 2, 3, 4)
+    # Call the function to get result
+    result = product_except_self(nums)  # Output should be [24, 12, 8, 6]
+    # Print the result
+    print(result.__str__())
+```