Describe an on logn algorithm for checking what is the

Question

Problem

1. Describe an O(n log(n)) algorithm for checking whether an array has duplicates.

2. What is the big-Oh running time of the following algorithm to find an element in an n × n array?

for (int i = 0; i < n; i++)
{
for (int j = 0; j < n; j++)
{
if (a[i][j] == value) {return false;}
}
}
return false;