题目链接
using namespace std;
const int maxn = 50+5;
double x[maxn],y[maxn],dist[maxn][maxn],d[maxn][maxn];
int main(){
int n;
while(scanf("%d",&n) == 1){
for(int i=1; i<=n; i++)
scanf("%lf%lf",&x[i],&y[i]);
for(int i=1; i<=n; i++)
for(int j=1; j<=n; j++)
dist[i][j] = sqrt((x[i]-x[j])*(x[i]-x[j])+(y[i]-y[j])*(y[i]-y[j]));
for(int i=n-1; i>=2; i--){
for(int j=1; j<i; j++){
if(i==n-1) d[i][j] = dist[j][n]+dist[i][n];
else d[i][j] = min(d[i+1][j]+dist[i][i+1],d[i+1][i]+dist[j][i+1]);
}
}
printf("%.2lf\n",dist[1][2]+d[2][1]);
}
}