Find the First Position with Balanced Side Sums

### Problem Return the leftmost index whose strictly-left sum equals its strictly-right sum. Exclude the indexed element itself. An empty side has sum zero. Return -1 if no position qualifies. ```cpp class Solution { public: int pivotIndex(vector<int>& nums); }; ``` ### Examples **Example 1:** ```text nums = [2,1,2] Output: 1 Explanation: Both side sums equal 2. ``` **Example 2:** ```text nums = [0,0] Output: 0 Explanation: Both positions qualify, so choose the first. ``` ### Constraints - Array size is between 1 and 10000. - Values lie in [-1000,1000]. ### Contract considerations Exclude the pivot itself and break ties toward the smallest index. ```hint Read the boundary condition Can the right-side sum be recovered from one total? ``` ### Boundary reminders Exclude the pivot itself and break ties toward the smallest index.