View Compilation Error

0_0_36122722_14185.cpp: In function 'int check(int, double)':
0_0_36122722_14185.cpp:59:34: error: 'qsort' was not declared in this scope
     qsort(px+1,n,sizeof(SPx),cmp2);
                                  ^
0_0_36122722_14185.cpp: In function 'int main()':
0_0_36122722_14185.cpp:84:37: error: 'qsort' was not declared in this scope
         qsort(sz+1,n,sizeof(SPt),cmp);
                                     ^