|洛谷|NOIP2010|搜索|P1378 油滴扩展

来源：互联网发布：ipad不能用淘宝怎么办编辑：程序博客网时间：2024/05/01 02:53

https://www.luogu.org/problem/show?pid=1378

比较简单，不过写错两个地方调了很久。。具体看代码

#include<cstdio>#include<algorithm>#include<cstring>#include<cmath>#define ms(i,j) memset(i,j, sizeof i);using namespace std;const double pi = 3.1415926535;int n;  int xa,xb,ya,yb;int xi[10], yi[10];double dis[10][10];int visit[10];double ans = 0.0;double r[10];double abss(double x) {return x>0?x:-x;} int dfs(int a, double s){    if (a > n)    {        ans = max(ans, s);//改正，之前min是错误的        return 0;    }    for (int i=1;i<=n;i++)    {        if (!visit[i])        {            visit[i] = true;            r[i] = min(min(abss(xi[i]-xa), abss(xi[i]-xb)),min(abss(yi[i]-ya), abss(yi[i]-yb)));            for (int j=1;j<=n;j++)            {                if (visit[j]&&j!=i)//<span style="font-family: Arial, Helvetica, sans-serif;">改正，</span><span style="font-family: Arial, Helvetica, sans-serif;">不是!visit[j]而是</span><span style="font-family: Arial, Helvetica, sans-serif;">visit[j]</span>                {                    r[i] = min(r[i], dis[i][j]-r[j]);                }            }             if (r[i]<=0) r[i] = 0;             dfs(a+1, s+pi*r[i]*r[i]);            visit[i] = false;        }    }}int main(){    scanf("%d%d%d%d%d", &n ,&xa,&ya,&xb,&yb);    for (int i=1;i<=n;i++)    {        scanf("%d%d", &xi[i], &yi[i]);    }    for (int i=1;i<=n;i++)    for (int j=1;j<=n;j++)    {        dis[i][j] = sqrt((xi[i]-xi[j])*(xi[i]-xi[j])+(yi[i]-yi[j])*(yi[i]-yi[j]));    }    ms(visit,false);    dfs(1, 0.0);    printf("%d", (int)(abss(xa-xb)*abss(ya-yb)) - (int)(ans+0.5));    return 0;}

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