foo.c: In function 'main':
foo.c:13:5: warning: implicit declaration of function 'qsort' [-Wimplicit-function-declaration]
     qsort(a,n,sizeof(a[0]),cmp);
     ^~~~~
foo.c:18:13: warning: implicit declaration of function 'abs' [-Wimplicit-function-declaration]
   sum1=sum1+abs(j-a[i]);
             ^~~

自豪的采用jd5进行评测(github.com/masnn/jd5)