[SGU]122. The book

Analysis

    这道题就是求一个图的哈密顿回路，给定的条件满足Ore性质，那么用《组合数学》上的构造方法来构造就可以了。

Accepted Code

var
    map:array[1..1000,1..1000] of boolean;
    used:array[1..1000] of boolean;
    chain,tmpchain:array[1..1000] of longint;
    bo:boolean;
    c:char;
    i,j,t,n,l,r,k,tmp:longint;

procedure print;
var
    i,l:longint;
begin
    for l:=1 to n do
        if chain[l]=1 then
            break;
    for i:=l to n do
        write(chain[i],' ');
    for i:=1 to l-1 do
        write(chain[i],' ');
    writeln(1);
end;

procedure reverse(i,j:longint);
var
    l:longint;
begin
    move(chain[i],tmpchain[1],(j-i+1)*sizeof(longint));
    for l:=i to j do
        chain[l]:=tmpchain[j-l+1];
end;

begin
    readln(n);
    for i:=1 to n do
        repeat
            read(t);
            map[i,t]:=true;
            map[t,i]:=true;
            read(c);
        until c<>' ';
    fillchar(used,sizeof(used),false);
    chain[1]:=1;
    used[1]:=true;
    t:=1;
    while t<n do
    begin
        for l:=1 to 2 do
        begin
            repeat
                bo:=true;
                for i:=1 to n do
                    if not used[i] and map[chain[t],i] then
                    begin
                        inc(t);
                        chain[t]:=i;
                        used[i]:=true;
                        bo:=false;
                        break;
                    end;
            until bo;
            reverse(1,t);
        end;
        for i:=1 to t-1 do
            if map[chain[1],chain[i+1]] and map[chain[i],chain[t]] then
            begin
                reverse(i+1,t);
                break;
            end;
        for i:=1 to n do
            if not used[i] then
            begin
                bo:=false;
                for l:=1 to t do
                    if map[i,chain[l]] then
                    begin
                        move(chain[1],tmpchain[1],l*sizeof(longint));
                        move(chain[l+1],chain[1],(t-l)*sizeof(longint));
                        move(tmpchain[1],chain[t-l+1],l*sizeof(longint));
                        inc(t);
                        chain[t]:=i;
                        used[i]:=true;
                        bo:=true;
                        break;
                    end;
                    if bo then
                        break;
            end;
    end;
    print;
end.