using System;
class Program
{
/*
Computes product of array except self.
nums = input array
size = number of elements
returns a new array containing the result
*/
static int[] ProductExceptSelf(int[] nums, int size) {
int[] answer = new int[size]; // allocate output array
int prefix = 1;
// ---- Prefix products ----
// answer[i] gets product of all elements before i
for (int i = 0; i < size; i++) {
answer[i] = prefix; // store prefix product
prefix *= nums[i]; // update prefix
// Example for nums = {5,2,3,4}:
// prefix values: 1, 5, 10, 30
}
// ---- Suffix products ----
// Multiply each answer[i] by product of all elements after i
int suffix = 1;
for (int i = size - 1; i >= 0; i--) {
answer[i] *= suffix; // combine prefix * suffix
suffix *= nums[i]; // update suffix
// suffix values: 1, 4, 12, 24, 120
// final answer: 24, 60, 40, 30
// 24 (24*1) 60 (12*5) 40 (10*4) 30 (30*1)
}
return answer;
}
static void Main()
{
int[] arr = { 5, 2, 3, 4 };
int size = arr.Length;
int[] result = ProductExceptSelf(arr, size);
Console.Write("Result: ");
for (int i = 0; i < size; i++) {
Console.Write(result[i] + " ");
}
}
}
/*
run:
Result: 24 60 40 30
*/
