# Find Pivot Index

Category

Prefix Sum

Checkbox

Checkbox

Difficulty

Easy

Index

19

Key Ideas

The key idea to solve the problem "Find Pivot Index" is to calculate the cumulative sum of the array and then iterate through the array to find the index where the sum of the elements to the left is equal to the sum of the elements to the right.

Problem Number

724

Problem Summary

The "Find Pivot Index" problem (Problem Number: 724) is an easy-level problem in the LeetCode-75 curated list. It falls under the category of Prefix Sum and involves finding the index in an array where the sum of elements on the left is equal to the sum of elements on the right. Some key pitfalls to watch out for are handling edge cases like an empty array or when no pivot index is found, and optimizing the solution to avoid unnecessary calculations by utilizing prefix sums efficiently.

Solution Summary

To solve the "Find Pivot Index" problem, we can use a prefix sum approach. First, we calculate the total sum of the given array. Then, we iterate through the array and maintain a left sum and a right sum. At each index, we check if the left sum is equal to the right sum (which is the total sum minus the left sum and the current element). If they are equal, we have found the pivot index. If no pivot index is found after iterating through the array, we return -1. The time complexity of this solution is O(n), where n is the length of the array.

Tags

Array

Prefix Sum