UVA1347 Tour 双调TSP

#include<bits/stdc++.h>
using namespace std;

const int maxn = 1001;
int x[maxn],y[maxn];

double dp[maxn][maxn];
bool vis[maxn][maxn];
#define Squ(x) ((x)*(x))

inline double dist(int a,int b)
{
    return sqrt(Squ(x[a]-x[b])+Squ(y[a]-y[b]));
}

int n;
double dfs(int i,int j)
{
    if(vis[i][j]) return dp[i][j];
    vis[i][j] = true;
    if(i == n-1){

        return dp[i][j] = dist(i,n)+dist(j,n);
    }
    return dp[i][j] = min(dfs(i+1,i)+dist(j,i+1),dfs(i+1,j)+dist(i,i+1));
}

int main()
{
   // freopen("in.txt","r",stdin);
    while(~scanf("%d",&n)){
        for(int i = 1; i <= n; i++) scanf("%d%d",x+i,y+i);
        memset(vis,0,sizeof(vis));
        double ans = dfs(1,1);
        printf("%.2lf\n",ans);
    }
    return 0;
}