模拟退火

#include<cstdio> 
#include<cstring>
#include<cmath>
#include<ctime>
#include<iostream>
#include<algorithm>
#include<queue>
#include<set>
#define inf (0x7fffffff)
#define l(a) ((a)<<1)
#define r(a) ((a)<<1|1)
#define b(a) (1<<(a))
#define T_min (1e-8)
#define R (0.99999)
#define e (2.718281828459045)
#define pi (3.14159265358979323846)
#define rep(i,a,b) for(int i=a;i<=(b);i++)
#define clr(a) memset(a,0,sizeof(a))
typedef long long ll;
typedef unsigned long long ull;
using namespace std;
int readint(){
    int t=0,f=1;char c=getchar();
    while(!isdigit(c)){
        if(c=='-') f=-1;
        c=getchar();
    }
    while(isdigit(c)){
        t=(t<<3)+(t<<1)+c-'0';
        c=getchar();
    }
    return t*f;
}
const int maxn=200009;
int n,opt,tmp,pre,del,path[2][maxn];
double T=1e5,d[maxn];
struct node{
    double x,y;
    inline bool operator<(const node A)const{
        return x<A.x||(x==A.x&&y<A.y);
    }
}X[maxn];
int dis(int i,int j){
     return int(sqrt((X[i].x-X[j].x)*(X[i].x-X[j].x)+(X[i].y-X[j].y)*(X[i].y-X[j].y))); 
}
int f(int t){
    int s=0;
    rep(i,2,n+1) s+=dis(path[t][i-1],path[t][i]);
    return s;
}
void newway(){
    int type=rand()%3,a=rand()%(n-1),b=rand()%(n-1);
    while(a==b) a=rand()%(n-1);a+=2;b+=2;
    if(a>b) swap(a,b);
    if(type==0){
        rep(i,1,n+1) path[opt^1][i]=path[opt][i];
        swap(path[opt^1][a],path[opt^1][b]);
    }else if(type==1){
        rep(i,1,a-1) path[opt^1][i]=path[opt][i];
        rep(i,a,b) path[opt^1][i]=path[opt][a-i+b];
        rep(i,b+1,n+1) path[opt^1][i]=path[opt][i];
    }else{
        rep(i,1,a-1) path[opt^1][i]=path[opt][i];
        path[opt^1][a]=path[opt][b];
        rep(i,a+1,b) path[opt^1][i]=path[opt][i-1];
        rep(i,b+1,n+1) path[opt^1][i]=path[opt][i];
    }
}
void cal(){
    int ans,cnt=0;
    srand(time(NULL));
    rep(i,1,n) path[opt][i]=i;path[opt][n+1]=1;ans=pre=f(opt);
    while(T>T_min){
        cnt++;if(cnt>1e6) break;
        newway();
        tmp=f(opt^1);del=tmp-pre;
        ans=min(ans,tmp);
        if(del<0){
            opt^=1;pre=tmp;
        }else if(rand()*rand()/32767.0/32767.0<pow(e,-del/T)){
            opt^=1;pre=tmp;
        }
        T*=R;
    }
    cout<<cnt<<endl;
    printf("%d
",ans);
}
int main(){
    freopen("#input.txt","r",stdin);
    //freopen("#output.txt","w",stdout);
    n=readint();
    rep(i,1,n){
        X[i].x=readint();X[i].y=readint();
    }
    cal();
    fclose(stdin);
    //fclose(stdout);
    return 0;
}