1064. Fixed Point

Given an array A of distinct integers sorted in ascending order, return the smallest index i that satisfies A[i] == i .  Return -1 if no such i exists.

 

Example 1:

Input: 

[-10,-5,0,3,7]

Output: 

3

Explanation: 

For the given array, 
A[0] = -10, A[1] = -5, A[2] = 0, A[3] = 3

, thus the output is 3.

Example 2:

Input: 

[0,2,5,8,17]

Output: 

0

Explanation: 

A[0] = 0

, thus the output is 0.

Example 3:

Input: 

[-10,-5,3,4,7,9]

Output: 

-1

Explanation: 

There is no such 
i

 that 
A[i] = i

, thus the output is -1.

 

Note:

1. 1 <= A.length < 10^4
2. -10^9 <= A[i] <= 10^9