P151PROG spoj PTIT – Xếp Hàng

const fi='; nmax=2*100000; type data=longint; var f:text; A,B,kq:array[0..nmax+1] of data; n,sodau,so1,so2:data; so:array[0..1000000] of data; procedure sort(l,r: longint); var i,j,x,y: longint; begin i:=l; j:=r; x:=a[(l+r) div 2]; repeat while a[i]<x do inc(i); while x<a[j] do dec(j); if not(i>j) then begin y:=a[i]; a[i]:=a[j]; a[j]:=y; y:=b[i]; b[i]:=b[j]; b[j]:=y; inc(i); j:=j-1; end; until i>j; if l<j then sort(l,j); if i<r then sort(i,r); end; procedure docfile; var i,j,dem:data; begin assign(f,fi); reset(f); readln(f,n); fillchar(so,sizeof(so),0); for i:=1 to n do begin readln(f,a[i],b[i]); so[a[i]]:=so[a[i]] xor 1; so[b[i]]:=so[b[i]] xor 1; end; for i:=0 to 1000000 do if so[i]<>0 then begin so1:=i; for j:=i+1 to 1000000 do if so[j]<>0 then begin so2:=j; break; end; break; end; close(f); end; function tknpA(x:data):data; var dau,cuoi,giua:data; begin dau:=1; cuoi:=n; while dau<=cuoi do begin giua:=(dau+cuoi) div 2; if A[giua]=X then exit(giua) else if x>a[giua] then dau:=giua+1 else cuoi:=giua-1; end; exit(0); end; procedure xuli; var i,j,x,dem,vt:data; begin sort(1,n); if tknpA(so1)<>0 then sodau:=so1 else sodau:=so2; //////////////// x:=B[1]; kq[2]:=x; dem:=2; repeat vt:=tknpA(x); if vt<=1 then break; inc(dem,2); kq[dem]:=B[vt]; x:=B[vt]; until false; x:=sodau; kq[1]:=x; dem:=1; repeat vt:=tknpA(x); if vt<=1 then break; inc(dem,2); kq[dem]:=B[vt]; x:=B[vt]; until false; for i:=1 to n do write(kq[i],' '); end; begin docfile; xuli; end.