Final answer:
To find the pivot index in an array, sum the array's total, iterate through, track cumulative sum, and compare with the rest. If an index is found where the left sum equals the right sum, that's the pivot index; otherwise, return -1.
Step-by-step explanation:
The student is asking how to find the pivot index in an array of integers, which is a typical programming or algorithmic problem that can be solved using mathematical concepts. In order to find the pivot index, you would need to iterate through the array while keeping track of the cumulative sum of the elements on the left and the total sum of all elements. The goal is to find an index where the left sum equals the sum of the elements to the right.
To achieve this, first calculate the total sum of the array. Then, iterate from the first element, maintaining a running sum of the elements processed so far. For each index, you can find the sum to the right by subtracting the running sum and the current element from the total sum. If at any point the running sum equals the sum to the right of the current index, then that index is the pivot index. If you reach the end of the array without finding such an index, then return -1 as no pivot index exists. It is essential to check the conditions at the edges of the array as well.
For example, for the array [1,7,3,6,5,6], the pivot index is 3 because the sum of the numbers strictly to the left of index 3 (1+7+3 = 11) is equal to the sum of the numbers strictly to the right of index 3 (5+6 = 11).
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