P5143攀爬者

#include<bits/stdc++.h> 
using namespace std;
int n;
struct t{
	int x,y,z;
}point[50001];
bool cmp(t a,t b){
	return a.z<=b.z;
}
int main(){
	cin>>n;
	for(int i=0;i<n;i++)cin>>point[i].x>>point[i].y>>point[i].z;
	sort(point,point+n,cmp);
	double m=0;
	for(int i=0;i<n-1;i++){
		m+=sqrt((point[i].x-point[i+1].x)*(point[i].x-point[i+1].x)+(point[i].y-point[i+1].y)*(point[i].y-point[i+1].y)+(point[i].z-point[i+1].z)*(point[i].z-point[i+1].z));
	}
	printf("%.3lf",m);
	return 0;
}