code里的dfs,

for(int i=1;i<=n+2;i++) vis[i]=0;

for(int i=1;i<=n+2;i++)for(int j=1;j<=i;j++)is[i][j]=is[j][i]=0;

if(z[i]-r<=0) is[i][n+1]=is[n+1][i]=1;
if(z[i]+r>=h) is[i][n+2]=is[n+2][i]=1;
for(int j=1;j<i;j++) if(dist(i,j)<=r*r*4) is[i][j]=is[j][i]=1;

dfs(n+1);
puts((vis[n+2])?"Yes":"No");

都是啥意思？