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Leetcode
Easy
Arrays
Smallest Stable Index I

Find the smallest index where the value equals the index.

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Problem Statement

Given an integer array nums, find the smallest index i such that nums[i] == i. If no such index exists, return -1.

This is a simple index-value matching problem: scan the array and look for the first position where the element is equal to its own index.

Input Format

  • An integer array nums.
  • The array is zero-indexed.

Output Format

  • Return the smallest index i such that nums[i] == i.
  • If no such index exists, return -1.

Constraints

  • 0 <= nums.length
  • Values in nums are integers.
  • Use a solution that is at least linear in the array size unless a stronger property is available.
Examples
Sample cases returned by the problem API.

Example 1

Input

nums = [0,2,3,4]

Output

0

Explanation

At index 0, nums[0] = 0, so the smallest stable index is 0.

Example 2

Input

nums = [1,2,3,4]

Output

-1

Explanation

No position has nums[i] == i.

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