implement of QuickSort

c code's runtime is about 65% of C++'s,In our test case, the length of
array is 100,000. And the program includes lots of input/output.
performance comparison of sort algorithm
Median of two array

MedianTwoArray.c: the input are sorted arrays with the same length
ref.c: check the validity of MedianTwoArray.c
add the SelectK algorithm