Find Peak Element
Find an index whose value is greater than both its neighbors, in O(log N).
Input format
The first line contains N. The second line contains N integers that strictly increase and then strictly decrease (either part may be empty), so there is exactly one peak.
Output format
Print the 0-based index of the peak element.
Constraints
- Values fit in a 64-bit signed integer
- Trailing whitespace and a trailing newline are ignored by the judge
Read from stdin, write to stdout. Sample cases below show the exact format.
Sample cases
Example 1
Input
5
1 3 8 4 2Expected output
2Example 2
Input
3
1 2 3Expected output
2