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Array of array products - dynamic programming algorithm - I got advice to declare variable leftToRight first, and then switch order of two statements of line 22 and line 24.
using System;
class Solution
{
public static int[] ArrayOfArrayProducts(int[] arr)
{
if(arr == null || arr.Length < 2)
return new int[0];
var length = arr.Length;
var product = new int[length];
for(int i = 0; i < length; i++)
{
product[i] = 1;
}
var leftToRight = 1;
// left to right, one multiplication
for(int i = 0; i < length; i++)
{
product[i] = leftToRight;
leftToRight *= arr[i];
}
// right to left, two multiplication
var rightToLeft = 1;
for(int i = length - 1; i >=0 ; i--)
{
product[i] *= rightToLeft;
rightToLeft *= arr[i];
}
return product;
}
static void Main(string[] args)
{
}
}
/*
dynamic programming
iteration -> left to right
product[]
for iteration
one multiplication
product[0] = 1
8, 10, 2
*8 *10
second iteration from right to left
for each iteration
two mulitiplcations
product[i] *= arr[i + 1] - two mulitiplcations
*/
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