Given a sorted array of distinct integer $A\left [ 1,2,....n \right ]$, the tightest upper bound to check the existence of any index $i$, for which $A[i]=i$ is equal to _______________
I thought here answer that mean time complexity will be $O(1),$ because directly getting the searching index and then checking if $A[i]=i$, but answer given as $O(log n).$Please help me out, which will be correct answer?
