Aimee

很水的题目

只是为了练练手

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cmath>
using namespace std;
int n;
struct b{
    double x;
    double y;
    double z;
}zn[500001];
bool cmp( b x,b y){
    return x.z<y.z;
} 
double now,ans;
double con(int x,int y){
    return sqrt((zn[x].x-zn[y].x)*(zn[x].x-zn[y].x)+(zn[x].y-zn[y].y)*(zn[x].y-zn[y].y)+(zn[x].z-zn[y].z)*(zn[x].z-zn[y].z));
} 
int main(){
    scanf("%d",&n);
    for(int i=1;i<=n;++i){
        scanf("%lf%lf%lf",&zn[i].x,&zn[i].y,&zn[i].z);
    }
    sort(zn+1,zn+n+1,cmp);
    for(int i=1;i<n;++i){
        ans+=con(i,i+1);
    }

    printf("%.3lf",ans);
    return 0;
}