prepare (1/3): 
finished

make (2/3): 
g++ -g -Wall -O2 -o main.o -c main.cpp 
main.cpp: In function 'int dselect(int*, int, int, int)':
main.cpp:110:13: warning: unused variable 'x' [-Wunused-variable]
         int x = dselect(a,p,p+(r-p)/5-1,(r-p)/10);
             ^
main.cpp: In function 'int main()':
main.cpp:152:41: warning: 'val' may be used uninitialized in this function [-Wmaybe-uninitialized]
   cout<<"The order-"<<order<<" item is "<<val;
   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~
g++ -g -Wall -O2 -o main main.o
finished

clean (3/3): 
finished

all task finished, build successfully