211. Find Pivot Index
Easy
Prefix Sum Balance
Array
Problem
Given an integer array nums, return the leftmost pivot index where the sum of elements strictly to the left equals the sum of elements strictly to the right. Return -1 if no pivot exists.
Examples
Example 1
Input: [1,7,3,6,5,6]
Output: 3
Example 2
Input: [1,2,3]
Output: -1
Example 3
Input: [2,1,-1]
Output: 0
Constraints
� 1 <= nums.length <= 10000
� -1000 <= nums[i] <= 1000
Hints
?? Compute the total sum once.
?? As you scan, derive the right sum from total - left - current.
Expected Complexity
Time: O(n)
Space: O(1)
Follow-up
Can you solve it without storing a prefix-sum array?
Practice Notes
Attempts: 0
Time spent: 0min
Hints used: 0
JavaScript
00:00
Loading...
Case 1
Case 2
Case 3
Input
[1,7,3,6,5,6]Expected
3