同时找出在数组中的最大值、最小值

If n is odd then initialize min and max as first element.

If n is even then initialize min and max as minimum and maximum of the first two elements respectively.

For rest of the elements, pick them in pairs and compare their

maximum and minimum with max and min respectively.

Time Complexity: O(n)

Total number of comparisons: Different for even and odd n, see below:

If n is odd:    3*(n-1)/2
If n is even:   1 Initial comparison for initializing min and max,
and 3(n-2)/2 comparisons for rest of the elements
=  1 + 3*(n-2)/2 = 3n/2 -2

http://www.geeksforgeeks.org/maximum-and-minimum-in-an-array/

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