Language: C++

#include <cstdio>

void dfs(int v)
{
	u[v]=true;
	o[k++]=v;
	for (int i=0; i<n; ++i)
		if (g[v][i] && !u[i]) dfs(i);
}

bool online(Point p,int i)
{
	return p==a[i] || p==b[ii] || p.x==a[i].x+b[i].x && p.y==a[i].y+b[i].y;
}

bool find(int dep)
{
	if (dep==k)
	{

	}
	for (int i=0; i<k; ++i)
		if (!used[i])
		{
			used[i]=true;
			q[dep]=o[i];
			if (find(dep+1)) return true;
			used[i]=false;
		}
}

int main()
{
	scanf("%d",&n);
	while (n)
	{
		for (i=0; i<n; ++i) scanf("%d%d%d%d",&a[i].x,&a[i].y,&b[i].x,&b[i].y);
		for (i=0; i<n; ++i)
			for (j=i+1; j<n; ++j)
				g[i][j]=g[j][i]=online(a[i],j) || online(b[i],j) || online(a[j],i) || online(b[j],i);
		memset(u,0,sizeof u);
		memset(ans,0,sizeof ans);
		for (i=0; i<n; ++i)
			if (!u[i])
			{
				k=0;
				dfs(i);
				find(0);
			}
		for (i=0; i<9; ++i) printf("%d ",ans[i]);
		printf("%d\n",ans[9]);
		scanf("%d",&n);
	}
	return 0;
}

Compiler output:
a.cc: In function 'void dfs(int)':
a.cc:5:9: error: 'u' was not declared in this scope
    5 |         u[v]=true;
      |         ^
a.cc:6:9: error: 'o' was not declared in this scope
    6 |         o[k++]=v;
      |         ^
a.cc:6:11: error: 'k' was not declared in this scope
    6 |         o[k++]=v;
      |           ^
a.cc:7:25: error: 'n' was not declared in this scope
    7 |         for (int i=0; i<n; ++i)
      |                         ^
a.cc:8:21: error: 'g' was not declared in this scope
    8 |                 if (g[v][i] && !u[i]) dfs(i);
      |                     ^
a.cc: At global scope:
a.cc:11:13: error: 'Point' was not declared in this scope; did you mean 'int'?
   11 | bool online(Point p,int i)
      |             ^~~~~
      |             int
a.cc:11:21: error: expected primary-expression before 'int'
   11 | bool online(Point p,int i)
      |                     ^~~
a.cc:11:26: error: expression list treated as compound expression in initializer [-fpermissive]
   11 | bool online(Point p,int i)
      |                          ^
a.cc: In function 'bool find(int)':
a.cc:18:18: error: 'k' was not declared in this scope
   18 |         if (dep==k)
      |                  ^
a.cc:22:25: error: 'k' was not declared in this scope
   22 |         for (int i=0; i<k; ++i)
      |                         ^
a.cc:23:22: error: 'used' was not declared in this scope
   23 |                 if (!used[i])
      |                      ^~~~
a.cc:26:25: error: 'q' was not declared in this scope
   26 |                         q[dep]=o[i];
      |                         ^
a.cc:26:32: error: 'o' was not declared in this scope
   26 |                         q[dep]=o[i];
      |                                ^
a.cc: In function 'int main()':
a.cc:34:21: error: 'n' was not declared in this scope
   34 |         scanf("%d",&n);
      |                     ^
a.cc:37:22: error: 'i' was not declared in this scope
   37 |                 for (i=0; i<n; ++i) scanf("%d%d%d%d",&a[i].x,&a[i].y,&b[i].x,&b[i].y);
      |                      ^
a.cc:37:55: error: 'a' was not declared in this scope
   37 |                 for (i=0; i<n; ++i) scanf("%d%d%d%d",&a[i].x,&a[i].y,&b[i].x,&b[i].y);
      |                                                       ^
a.cc:37:71: error: 'b' was not declared in this scope
   37 |                 for (i=0; i<n; ++i) scanf("%d%d%d%d",&a[i].x,&a[i].y,&b[i].x,&b[i].y);
      |                                                                       ^
a.cc:38:22: error: 'i' was not declared in this scope
   38 |                 for (i=0; i<n; ++i)
      |                      ^
a.cc:39:30: error: 'j' was not declared in this scope
   39 |                         for (j=i+1; j<n; ++j)
      |                              ^
a.cc:40:33: error: 'g' was not declared in this scope
   40 |                                 g[i][j]=g[j][i]=online(a[i],j) || online(b[i],j) || online(a[j],i) || online(b[j],i);
      |                                 ^
a.cc:40:56: error: 'a' was not declared in this scope
   40 |                                 g[i][j]=g[j][i]=online(a[i],j) || online(b[i],j) || online(a[j],i) || online(b[j],i);
      |                                                        ^
a.cc:40:55: error: 'online' cannot be used as a function
   40 |                                 g[i][j]=g[j][i]=online(a[i],j) || online(b[i],j) || online(a[j],i) || online(b[j],i);
      |                                                 ~~~~~~^~~~~~~~
a.cc:40:74: error: 'b' was not declared in this scope
   40 |                                 g[i][j]=g[j][i]=online(a[i],j) || online(b[i],j) || online(a[j],i) || online(b[j],i);
      |                                                                          ^
a.cc:40:73: error: 'online' cannot be used as a function
   40 |                                 g[i][j]=g[j][i]=online(a[i],j) || online(b[i],j) || online(a[j],i) || online(b[j],i);
      |                                                                   ~~~~~~^~~~~~~~
a.cc:40:91: error: 'online' cannot be used as a function
   40 |                                 g[i][j]=g[j][i]=online(a[i],j) || online(b[i],j) || online(a[j],i) || online(b[j],i);
      |                                                                                     ~~~~~~^~~~~~~~
a.cc:40:109: error: 'online' cannot be used as a function
   40 |                                 g[i][j]=g[j][i]=online(a[i],j) || online(b[i],j) || online(a[j],i) || online(b[j],i);
      |                                                                                                       ~~~~~~^~~~~~~~
a.cc:41:24: error: 'u' was not declared in this scope
   41 |                 memset(u,0,sizeof u);
      |                        ^
a.cc:41:17: error: 'memset' was not declared in this scope
   41 |                 memset(u,0,sizeof u);
      |                 ^~~~~~
a.cc:2:1: note: 'memset' is defined in header '<cstring>'; this is probably fixable by adding '#include <cstring>'
    1 | #include <cstdio>
  +++ |+#include <cstring>
    2 | 
a.cc:42:24: error: 'ans' was not declared in this scope
   42 |                 memset(ans,0,sizeof ans);
      |                        ^~~
a.cc:43:22: error: 'i' was not declared in this scope
   43 |                 for (i=0; i<n; ++i)
      |                      ^
a.cc:46:33: error: 'k' was not declared in this scope
   46 |                                 k=0;
      |                                 ^
a.cc:50:22: error: 'i' was not declared in this scope
   50 |                 for (i=0; i<9; ++i) printf("%d ",ans[i]);
      |                      ^
a.cc: In function 'bool find(int)':
a.cc:30:1: warning: control reaches end of non-void function [-Wreturn-type]
   30 | }
      | ^