bzoj 1002 找规律（基尔霍夫矩阵）

　　网上说的是什么基尔霍夫矩阵，没学过这个，打个表找下规律，发现

w[i]=3*w[i-1]-w[i-2]+2;

然后写个高精直接递推就行了

//By BLADEVIL

var

    n                    :longint;

    a, b, c                :array[0..100000] of longint;

    w                    :array[0..200] of ansistring;

    i                    :longint;

    

function plus(s1,s2:ansistring):ansistring;

var

    len                    :longint;

    i                    :longint;

    s                    :ansistring;

    

begin

    fillchar(a,sizeof(a),0);

    fillchar(b,sizeof(b),0);

    fillchar(c,sizeof(c),0);

    len:=length(s1);

    for i:=1 to len do a[(len-i) div 4+1]:=a[(len-i) div 4+1]*10+ord(s1[i])-48;

    len:=length(s2);

    for i:=1 to len do b[(len-i) div 4+1]:=b[(len-i) div 4+1]*10+ord(s2[i])-48;

    if length(s1)>len then len:=length(s1);

    len:=(len+3) div 4;

    for i:=1 to len do

    begin

        c[i]:=c[i]+a[i]+b[i];

        c[i+1]:=c[i+1]+c[i] div 10000;

        c[i]:=c[i] mod 10000;

    end;

    inc(len);

    plus:='';

    for i:=len downto 1 do 

    begin

        str(c[i],s);

        if c[i]<1000 then plus:=plus+'0';

        if c[i]<100 then plus:=plus+'0';

        if c[i]<10 then plus:=plus+'0';

        plus:=plus+s;

    end;

    while (plus[1]='0') and (length(plus)>1) do delete(plus,1,1);

end;

    

function jian(s1,s2:ansistring):ansistring;

var

    len                    :longint;

    i                    :longint;

    s                    :ansistring;

begin

    fillchar(a,sizeof(a),0);

    fillchar(b,sizeof(b),0);

    fillchar(c,sizeof(c),0);

    len:=length(s1);

    for i:=1 to len do a[(len-i) div 4+1]:=a[(len-i) div 4+1]*10+ord(s1[i])-48;

    len:=length(s2);

    for i:=1 to len do b[(len-i) div 4+1]:=b[(len-i) div 4+1]*10+ord(s2[i])-48;

    len:=(length(s1)+3) div 4;

    for i:=1 to len do c[i]:=a[i]-b[i];

    for i:=1 to len do if c[i]<0 then  

    begin

        c[i]:=c[i]+10000;

        dec(c[i+1]);

    end;

    jian:='';

    for i:=len downto 1 do

    begin

        str(c[i],s);

        if c[i]<1000 then jian:=jian+'0';

        if c[i]<100 then jian:=jian+'0';

        if c[i]<10 then jian:=jian+'0';

        jian:=jian+s;

    end;

    while (jian[1]='0') and (length(jian)>1) do delete(jian,1,1);

end;

    

begin

    read(n);

    w[1]:='1'; w[2]:='5';

    for i:=3 to n do 

        w[i]:=plus(jian(plus(plus(w[i-1],w[i-1]),w[i-1]),w[i-2]),'2');

    writeln(w[n]);

end.