定义状态dp[i][j]表示一个人到i，一个人到j，保证i>j

然后倒着推

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

const int maxn = 1e3+10;

struct node {
    int x,y;
}point[maxn];

double dis(int a,int b) {
    return sqrt(pow((point[a].x-point[b].x),2)+pow(point[a].y-point[b].y,2));
}

double dp[maxn][maxn];

int n;

int main() {
    freopen("in.txt","r",stdin);
    while(scanf("%d",&n)!=EOF) {
        for(int i=1;i<=n;i++) {
            scanf("%d%d",&point[i].x,&point[i].y);
        }
        memset(dp,0x43,sizeof(dp));
        for(int i=n-1;i>1;i--)
            for(int j=1;j<i;j++) {
                if(i==n-1) dp[i][j]=dis(n-1,n)+dis(j,n);
                else dp[i][j]=min(dp[i+1][j]+dis(i,i+1),dp[i+1][i]+dis(j,i+1));
            }
        printf("%.2f\n",dp[2][1]+dis(1,2));
    }
    return 0;
}

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