#724
Find Pivot Index
pupil · 365 · lc easy +23 · verified · 62.2% accepted · 9,248 likes · top 63%
Description
Given an integer array nums, find the leftmost pivot index — the index at which the sum of all elements strictly to its left equals the sum of all elements strictly to its right. Boundary indices treat the missing side as sum 0. Return the leftmost such index, or -1 if none exists.
Example 1:
Input: nums = [1,7,3,6,5,6]
Output: 3
Explanation:
The pivot index is 3.
Left sum = nums[0] + nums[1] + nums[2] = 1 + 7 + 3 = 11
Right sum = nums[4] + nums[5] = 5 + 6 = 11
Example 2:
Input: nums = [1,2,3]
Output: -1
Explanation:
There is no index that satisfies the conditions in the problem statement.
Example 3:
Input: nums = [2,1,-1]
Output: 0
Explanation:
The pivot index is 0.
Left sum = 0 (no elements to the left of index 0)
Right sum = nums[1] + nums[2] = 1 + -1 = 0
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