1679: [Usaco2005 Jan]Moo Volume 牛的呼声
Time Limit: 1 Sec Memory Limit: 64 MB
Submit: 723 Solved: 346
[Submit][Status]
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
* Line 1: A single integer, the total volume of all the MOOs.
Sample Input
1
5
3
2
4
INPUT DETAILS:
There are five cows at locations 1, 5, 3, 2, and 4.
Sample Output
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.
HINT
Source
#include<cstdio>
#include<cstdlib>
#include<cmath>
#include<cstring>
#include<algorithm>
#include<iostream>
#include<vector>
#include<map>
#include<set>
#include<queue>
#define inf 1000000000
#define maxn 10000+100
#define maxm 100000+100
#define ll long long
using namespace std;
inline ll read()
{
ll x=,f=;char ch=getchar();
while(ch<''||ch>''){if(ch=='-')f=-;ch=getchar();}
while(ch>=''&&ch<=''){x=*x+ch-'';ch=getchar();}
return x*f;
}
ll a[maxn];
int main()
{
freopen("input.txt","r",stdin);
freopen("output.txt","w",stdout);
ll n=read(),ans=,sum;
for(int i=;i<=n;i++)a[i]=read();
sort(a+,a+n+);sum=a[];
for(int i=;i<=n;i++)
{
ans+=(a[i]*(i-))-sum;sum+=a[i];
}
printf("%lld\n",*ans);
return ;
}