POJ 2231 Moo Volume

Description

Farmer John has received a noise complaint from his neighbor, Farmer Bob, stating that his cows are making too much noise. 

FJ's N cows (1 <= N <= 10,000) all graze at various locations on a long one-dimensional pasture. The cows are very chatty animals. Every pair of cows simultaneously carries on a conversation (so every cow is simultaneously MOOing at all of the N-1 other cows). When cow i MOOs at cow j, the volume of this MOO must be equal to the distance between i and j, in order for j to be able to hear the MOO at all. Please help FJ compute the total volume of sound being generated by all N*(N-1) simultaneous MOOing sessions.

Input

* Line 1: N 

* Lines 2..N+1: The location of each cow (in the range 0..1,000,000,000).

Output

There are five cows at locations 1, 5, 3, 2, and 4.

Sample Input

515324

Sample Output

40

Hint

INPUT DETAILS: 

There are five cows at locations 1, 5, 3, 2, and 4. 

OUTPUT DETAILS: 

Cow at 1 contributes 1+2+3+4=10, cow at 5 contributes 4+3+2+1=10, cow at 3 contributes 2+1+1+2=6, cow at 2 contributes 1+1+2+3=7, and cow at 4 contributes 3+2+1+1=7. The total volume is (10+10+6+7+7) = 40.

求个和，简单题

#include<stack>#include<cmath>#include<queue>#include<vector>#include<cstdio>#include<cstring>#include<algorithm>using namespace std;typedef long long ll;const ll maxn=100005;ll T,n,m,a[maxn],ans,sum;int main(){while (~scanf("%lld",&n)){ans=sum=0;for (ll i=1;i<=n;i++) {scanf("%lld",&a[i]);sum+=a[i];}sort(a+1,a+n+1);for (ll i=1;i<=n;i++){ans+=sum-a[i]*(n-i+1);sum-=a[i];}printf("%lld\n",ans+ans);}return 0;}