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Index of first 1 in a sorted array of 0s and 1s
Basic Accuracy: 42.86% Submissions: 91 Points: 1

Given a sorted array consisting 0’s and 1’s. The task is to find the index of first ‘1’ in the given array.

 

Example 1:

Input : 
arr[] = {0, 0, 0, 0, 0, 0, 1, 1, 1, 1}
Output : 
6
Explanation:
The index of first 1 in the array is 6.


Example 2:
Input : 
arr[] = {0, 0, 0, 0}
Output : 
-1
Explanation:
1's are not present in the array.
 
 

Your Task:  
You don't need to read input or print anything. Your task is to complete the function firstIndex() which takes the array A[] and its size N as inputs and returns the index of first 1. If 1 is not present in the array then return -1.


Expected Time Complexity: O(Log (N))
Expected Auxiliary Space: O(1)

 

Constraints:
1 ≤ N ≤ 108
0 ≤ Ai ≤ 1

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Index of first 1 in a sorted array of 0s and 1s

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