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What this problem traveling salesman problem legend called?

This title search and note cards violent search, note ......

#include<bits/stdc++.h>
using namespace std;
const int maxn=20;
int n,vis[maxn];
double x[maxn],y[maxn],ans,dist[maxn][maxn];
double dp[1<<16][maxn];
int main(){
    cin>>n;
    for(int i=1;i<=n;i++)
        cin>>x[i]>>y[i];
    x[0]=y[0]=0;
    for(int i=0;i<=n;i++)
        for(int j=0;j<=n;j++)
            dist[i][j]=sqrt((x[i]-x[j])*(x[i]-x[j])+(y[i]-y[j])*(y[i]-y[j]));
    memset(dp,127,sizeof(dp));
    for(int i=0;i<=n;i++)
        dp[(1<<(n+1))-1][i]=0;
    for(int S=(1<<(n+1))-2;~S;S--)
        for(int i=0;i<=n;i++)
            for(int j=0;j<=n;j++)
                if(!(S&1<<j))dp[S][i]=min(dp[S][i],dp[S|1<<j][j]+dist[i][j]);
    printf("%.2lf\n",dp[0][0]);
    return 0;
}

Deeply felt small and weak.