数据结构暑期自学--MOOC浙江大学pta(7-10 Saving James Bond - Easy Version)

典型的dfs,根据视频里的想法来写

1、第一跳要单独判断（firstjump）

2、因为题目要求的是求是否能到岸上，所以一旦可以到岸上，就停止dfs

# include 
# include 
# include  
int n, d;
int g[200][3];
int visited[200];
int answer;
int firstjump(int x)
{
	double ju = sqrt(g[x][1]*g[x][1]+g[x][2]*g[x][2]);
	if (ju<=7.5+d)
	return 1;
	else
	return 0;
}
int issave(int x)
{
	if ((g[x][1]-d<=-50)||(g[x][1]+d)>=50||(g[x][2]-d<=-50)||(g[x][2]+d)>=50)
	return 1;
	else
	return 0;
}
int jump(int x, int y)
{
	double ju = sqrt((g[x][1]-g[y][1])*(g[x][1]-g[y][1])+(g[x][2]-g[y][2])*(g[x][2]-g[y][2]));
	if (ju<=d)
	return 1;
	else
	return 0;
}
int DFS(int x)
{
	visited[x] = 1;
	if (issave(x))
	answer = 1;
	else
	{
		for (int i=1; i<=n; i++)
		{
			if (!visited[i]&&jump(x, i))
			{
				answer = DFS(i);
				if (answer==1)
				break;
			}
		}
	}
	return answer;
}
int main()
{
	scanf("%d%d", &n, &d);
	for (int i=1; i<=n; i++)
	{
		scanf("%d%d", &g[i][1], &g[i][2]);
	}
	for (int i=1; i<=n; i++)
	{
		if (!visited[i]&&firstjump(i))
		{
			answer = DFS(i);
			if (answer == 1)
			{
				printf("Yesn");
				break;
			}
		}
	} 
	if (answer==0)
	{
		printf("Non");
	}
	return 0;
}