版权声明：https://blog.csdn.net/qq_41730082 https://blog.csdn.net/qq_41730082/article/details/85778932
题目链接（不止是C++、G++也是能过的）
题意：一开始压根没读懂题意，可能就是因为把半径和直径看错了。
在中心岛为（0，0）直径为15的岛上，就是主人公的位置了，然后，我们的整个逃生区域是（-50，-50）为左下角，（50，50）为右下角的这么一个区域，只需要跑出这个区域，就是赢了，所以，我们只需要建两个虚点：（一）、中心岛的点；（二）、区域外的点。以此跑Dijkstra即可。
#include <iostream>
#include <cstdio>
#include <cmath>
#include <string>
#include <cstring>
#include <algorithm>
#include <limits>
#include <vector>
#include <stack>
#include <queue>
#include <set>
#include <map>
#define lowbit(x) ( x&(-x) )
#define pi 3.141592653589793
#define e 2.718281828459045
//#define INF 0x3f3f3f3f
#define efs 1e-7
using namespace std;
typedef unsigned long long ull;
typedef long long ll;
const int maxN = 105;
const double INF = 1e9 + 7.;
int N, head[maxN], cnt, step[maxN];
double D, mp[maxN][maxN], dis[maxN];
struct node
{
double x, y;
node(double a=0, double b=0):x(a), y(b) {}
}a[maxN];
double Dis(int i, int j) { return sqrt((a[i].x - a[j].x) * (a[i].x - a[j].x) + (a[i].y - a[j].y) * (a[i].y - a[j].y)); }
struct Eddge
{
int nex, to;
double val;
Eddge(int a=0, int b=0, double c=0):nex(a), to(b), val(c) {}
}edge[maxN*maxN];
inline void addEddge(int u, int v, double val)
{
edge[cnt] = Eddge(head[u], v, val);
head[u] = cnt++;
}
inline double Min_4(double e1, double e2, double e3, double e4) { return min(min(e1, e2), min(e3, e4)); }
struct point
{
int id, step;
double val;
point(int a=0, double b=0, int c=0):id(a), val(b), step(c) {}
friend bool operator < (point e1, point e2)
{
if(e1.val == e2.val) return e1.step > e2.step;
return e1.val > e2.val;
}
};
void Dijkstra(int pos)
{
priority_queue<point> Q;
Q.push(point(pos, 0, 0));
dis[pos] = 0.;
step[pos] = 0;
while(!Q.empty())
{
point tmp = Q.top(); Q.pop();
int u = tmp.id;
for(int i=head[u]; i!=-1; i=edge[i].nex)
{
int v = edge[i].to;
double cost = edge[i].val;
if(dis[v] > dis[u] + cost)
{
dis[v] = dis[u] + cost;
step[v] = step[u] + 1;
Q.push(point(v, dis[v], step[v]));
}
else if(dis[v] >= dis[u] + cost + efs && step[v] > step[u] + 1)
{
step[v] = step[u] + 1;
Q.push(point(v, dis[v], step[v]));
}
}
}
}
inline void init()
{
a[0] = node();
cnt = 0;
memset(head, -1, sizeof(head));
for(int i=0; i<=N+1; i++)
{
dis[i] = INF;
step[i] = 0;
}
}
int main()
{
while(scanf("%d%lf", &N, &D)!=EOF)
{
init();
for(int i=1; i<=N; i++)
{
double tmp = 0.;
scanf("%lf%lf", &a[i].x, &a[i].y);
if(Dis(0, i) < 7.5 + efs || a[i].x > 50. || a[i].x < -50. || a[i].y > 50. || a[i].y < -50.) continue;
for(int j=1; j<i; j++)
{
if((tmp = Dis(i, j)) <= D + efs)
{
addEddge(i, j, tmp);
addEddge(j, i, tmp);
}
}
if((tmp = Dis(0, i) - 7.5) <= D + efs) addEddge(0, i, tmp);
if((tmp = Min_4(a[i].x + 50, a[i].y + 50, 50 - a[i].x, 50 - a[i].y)) <= D + efs) addEddge(i, N + 1, tmp);
}
Dijkstra(0);
if(dis[N+1] < INF) printf("%.2lf %d\n", dis[N+1], step[N+1]);
else printf("can't be saved\n");
}
return 0;
}