tapeEqualibrium.js

function tapeEquilibrium(A) {
    var p, i;
    var leftSum = 0, rightSum = 0;
    var totalSum = 0;
    var lastMin, currentMin;
    var leng = A.length;
    
    if (leng == 2) { return Math.abs(A[0] - A[1]); }
    if (leng == 1) { return Math.abs(A[0]); }
    //edge cases where the length is 1 or 2
    
    //iterate once to get the total sum of the array
    for (i=0; i < leng; i++) {
        totalSum = totalSum + A[i];
    }
    //sets the minimum value to the totalSum minus the first element twice
    //twice because the total includes the value (first), then we subtract that new total (second)
    lastMin = Math.abs(totalSum - A[0] - A[0]);
    
    //excludes the first and last element of the array
    //iterates
    for (p = 1; p <= leng-1; p++) {
        leftSum += A[p - 1];
        //left sum is initally zero, but now is the sum of all the values to the left of the pointer
        
        rightSum = totalSum - leftSum;
        //using the left sum to determine the right sum
        
        currentMin = Math.abs(leftSum - rightSum);
        //determines the currentMin
        
        lastMin = (currentMin < lastMin) ? currentMin : lastMin;
        //lastMin is a global variable that is redefined
    }
    
    return lastMin;    
}