【洛谷1433】吃奶酪 搜索+剪枝

AC代码

#include <bits/stdc++.h>

using namespace std;

#define ms(a,b) memset(a,b,sizeof(a))

typedef long long ll;

struct Point{
    double x,y;
}point[20];

int n;
double dist[20][20];
double ans;
int vis[20];

inline int read()
{
    int X=0,w=0; char ch=0;
    while(!isdigit(ch))
    {
        w|=ch=='-';
        ch=getchar();
    }
    while(isdigit(ch))
    {
        X=(X<<3)+(X<<1)+(ch^48);
        ch=getchar();
    }
    return w?-X:X;
}

double dist_calc(double x1,double y1,double x2,double y2) 
{
    return sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
}

void dfs(double x,double y,int num,double distnow,int now) 
{
    if (distnow>ans) return;
    if (num==n) 
    {
        ans=min(ans,distnow);
        return;
    }
    for (int i=1;i<=n;i++) 
    {
        if ( vis[i] ) 
        { 
            vis[i] = 0;
            dfs(point[i].x,point[i].y,num+1,distnow+dist[now][i],i);
            vis[i] = 1;
        }
    }
}

int main()
{
    n=read();
    point[0].x=0,point[0].y=0;
    for (int i=1;i<=n;i++) 
    {
        cin>>point[i].x>>point[i].y; 
    }
    for (int i=1;i<=n;i++) 
    {
        for (int j=1;j<=n;j++) 
        {
            dist[i][j]=dist_calc(point[i].x,point[i].y,point[j].x,point[j].y);
        }
    }
    for (int i=1;i<=n;i++) dist[0][i]=dist[i][0]=dist_calc(0,0,point[i].x,point[i].y);
    vis[0]=0;
    ms( vis, 1);
    ans=1<<30; dfs(0,0,0,0,0);  
    printf("%0.2lf
",ans);
    return 0;
}