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.
约翰的邻居鲍勃控告约翰家的牛们太会叫.
约翰的N(1≤N≤10000)只牛在一维的草场上的不同地点吃着草.她们都是些爱说闲话的奶牛,每一只同时与其他N-1只牛聊着天.一个对话的进行,需要两只牛都按照和她们间距离等大的音量吼叫,因此草场上存在着N(N-1)/2个声音. 请计算这些音量的和.
* Line 1: N * Lines 2..N+1: The location of each cow (in the range 0..1,000,000,000).
第1行输入N,接下来输入N个整数,表示一只牛所在的位置.
* Line 1: A single integer, the total volume of all the MOOs.
一个整数,表示总音量.
#include <cstdio>
#include <algorithm>
using namespace std;
int n;
long long x[10000 + 10];
int main(){
scanf("%d", &n);
for(int i = 1; i <= n; i++) scanf("%d", x + i);
sort(x + 1, x + n + 1);
long long ans = 0;
for(int i = 2; i <= n; i++)
ans += (x[i] - x[i - 1]) * (i - 1) * (n - i + 1);
printf("%lld\n", ans * 2);
return 0;
}