欧拉回路——欧拉路与欧拉回路

program zht;
var
n,m,i,p,max,tn,x,y,s:longint;
d,bh:array[0..50] of longint;
a:array[0..2000] of longint;
map1,map2:array[0..50,0..50] of longint;

procedure dfs1(x:longint);
var
i:longint;
begin
for i:=1 to n do
 if map1[x,i]>0 then begin
 dec(map1[x,i]);
 dec(map1[i,x]);
 dfs1(i);
 end;
 inc(tn);
 a[tn]:=x;
end;

procedure dfs2(x:longint);
var
i:longint;
begin
for i:=1 to n do
 if map2[x,i]>0 then begin
 dec(map2[x,i]);
 dec(map2[i,x]);
 dfs2(i);
 end;
 inc(tn);
 a[tn]:=x;
end;

procedure chuli1;
var
k:longint;
begin
k:=0;

dfs1(1);
for k:=tn downto 1 do
write(a[k],‘ ‘);

end;

procedure chuli2;
var
k:longint;
begin
k:=0;

dfs2(max);

for k:=tn downto 1 do
inc(bh[a[k]]);

for k:=tn downto 1 do
write(a[k],‘ ‘);

end;


begin
assign(input,‘path_euler.in‘);
assign(output,‘path_euler.out‘);
reset(input);
rewrite(output);

readln(n,m);

for i:=1 to m do
begin
readln(x,y);
inc(map1[x,y]);
inc(map1[y,x]);
inc(map2[x,y]);
inc(map2[y,x]);
inc(d[x]);
inc(d[y]);
end;

for i:=1 to n do
if (d[i]=0) or (d[i] mod 2=1) then begin p:=1; break; end;

for i:=1 to n do
if d[i] mod 2=1 then begin
 if i>max then max:=i;
 inc(s);
 end;

if (s<>2) and (p=1) then begin writeln(‘-1‘); exit; end;

if p=0 then chuli1
else chuli2;

close(input);
close(output);

end.