How to optimally divide an array into two subarrays so that sum of elements in both are same, otherwise give an error?

Question

How to optimally divide an array into two subarrays so that sum of elements in both subarrays is same, otherwise give an error?

Example 1

Given the array

Answer 1

I was asked this question in an interview, and I gave below simple solution, as I had NOT seen this problem in any websiteS earlier.

Lets say Array A = {45,10,10,10,10,5} Then, the split will be at index = 1 (0-based index) so that we have two equal sum set {45} and {10,10,10,10,5}

int leftSum = A[0], rightSum = A[A.length - 1];
int currentLeftIndex = 0; currentRightIndex = A.length - 1

/* Move the two index pointers towards mid of the array untill currentRightIndex != currentLeftIndex. Increase leftIndex if sum of left elements is still less than or equal to sum of elements in right of 'rightIndex'.At the end,check if leftSum == rightSum. If true, we got the index as currentLeftIndex+1(or simply currentRightIndex, as currentRightIndex will be equal to currentLeftIndex+1 in this case). */

while (currentLeftIndex < currentRightIndex)
{
if ( currentLeftIndex+1 != currentRightIndex && (leftSum + A[currentLeftIndex + 1)     <=currentRightSum )
{
 currentLeftIndex ++;
 leftSum = leftSum + A[currentLeftIndex];
}


if ( currentRightIndex - 1 != currentLeftIndex && (rightSum + A[currentRightIndex - 1] <= currentLeftSum)
{
 currentRightIndex --;
 rightSum = rightSum + A[currentRightIndex];
}

}

if (CurrentLeftIndex == currentRightIndex - 1 && leftSum == rightSum)
PRINT("got split point at index "+currentRightIndex);