Haha, guys. Guess what. I cheated on the online judge and she accepted the following 1/2*N*(N-1) algorithm !!!

181b with gcc
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2373307 hjin 2231 Accepted 76K 873MS GCC 181B 2007-07-22 21:38:11 

程序代码:

main(){int N,i,j,c[10000];long long s;while(scanf("%d",&N)!=-1){s=0ll;for(i=0;i<N;++i){scanf("%d",c+i);for(j=0;j<i;++j)s+=c[i]>c[j]?c[i]-c[j]:c[j]-c[i];}s<<=1;printf("%I64d\n",s);}}