Problem Statement

Given an integer array nums, return the leftmost middleIndex (i.e., the smallest amongst all the possible ones).

A middleIndex is an index where the sum of the numbers to the left of this index is equal to the sum of the numbers to the right of this index.

You can consider the left sum 0 for middleIndex == 0, and right sum 0 for middleIndex == nums.length - 1.

If no middleIndex exists in nums, return -1.

Examples

Example 1:

• Input: nums = [1, 7, 3, 6, 5, 6]
• Expected Output: 3
• Justification: The sum of the numbers to the left of index 3 (1 + 7 + 3 = 11) is equal to the sum of the numbers to the right of index 3 (5 + 6 = 11).

Example 2:

• Input: nums = [2, 1, -1]
• Expected Output: 0
• Justification: The sum of the numbers to the left of index 0 is considered to be 0. The sum of the numbers to the right of index 0 (1 + -1 = 0) is also 0.

Example 3:

• Input: nums = [2, 3, 5, 5, 3, 2]
• Expected Output: -1
• Justification: There is no middleIndex exists in the array.

Constraints:

• 1 <= nums.length <= 100
• -1000 <= nums[i] <= 1000

Try it yourself

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