[BZOJ1180] [CROATIAN2009]OTOCI

传送门

http://www.lydsy.com/JudgeOnline/problem.php?id=1180

题目大意

连边+单点修改+路径和

题解

LCT
终于意识到LCT的可怕之处了
细节！！！

const    maxn=30000;var    son:array[0..maxn,1..2]of longint;    fa,val,sum,rev:array[0..maxn]of longint;    i,j,k:longint;    n,m,a,b:longint;    cha,ch:char;procedure swap(var a,b:longint);var c:longint;begin c:=a; a:=b; b:=c; end;procedure pushdown(a:longint);begin    if a=0 then exit;    if rev[a]=0 then exit;    swap(son[a,1],son[a,2]);    if son[a,1]<>0 then rev[son[a,1]]:=rev[son[a,1]] xor 1;    if son[a,2]<>0 then rev[son[a,2]]:=rev[son[a,2]] xor 1;     rev[a]:=rev[a] xor 1;end;procedure update(a:longint);begin    if a=0 then exit;    sum[a]:=sum[son[a,1]]+sum[son[a,2]]+val[a];end;function isroot(a:longint):longint;begin if (son[fa[a],1]<>a)and(son[fa[a],2]<>a) then exit(1) else exit(0); end;procedure rotate(a,kind:longint);var b,c,unkind:longint;begin    b:=fa[a]; c:=fa[b]; unkind:=kind xor 3;    if son[c,1]=b then son[c,1]:=a else    if son[c,2]=b then son[c,2]:=a;     fa[son[a,unkind]]:=b; son[b,kind]:=son[a,unkind]; son[a,unkind]:=b;    fa[b]:=a; fa[a]:=c;    update(b); update(a);end;procedure splay(a:longint);var b,kind,unkind:longint;begin    pushdown(a);     while isroot(a)=0 do        begin            b:=fa[a]; pushdown(fa[b]); pushdown(b); pushdown(a);            if son[b,1]=a then kind:=1 else kind:=2; unkind:=kind xor 3;            if isroot(b)=1 then rotate(a,kind)            else                if son[fa[b],kind]=b                then begin rotate(b,kind); rotate(a,kind); end                else begin rotate(a,kind); rotate(a,unkind); end;        end;end;procedure access(a:longint);var b:longint;begin    splay(a); son[a,2]:=0; update(a);    while fa[a]<>0 do        begin            b:=fa[a];            splay(b);            son[b,2]:=a;             update(b);            splay(a);        end;end;procedure makeroot(a:longint);begin    access(a);    rev[a]:=rev[a] xor 1;    pushdown(a);end;function getroot(a:longint):Longint;begin    access(a);    while son[a,1]<>0 do        a:=son[a,1];    exit(a);end;procedure link(a,b:longint);begin    makeroot(a);    fa[a]:=b;end;procedure work1(a,b:longint);begin    if getroot(a)=getroot(b)    then writeln('no')    else begin writeln('yes'); link(a,b); end;end;procedure work2(a,b:longint);begin    access(a);    val[a]:=b;    update(a);end;procedure work3(a,b:longint);begin    if getroot(a)<>getroot(b)    then writeln('impossible')    else begin makeroot(a); access(b); writeln(sum[b]); end;end;begin    readln(n);    for i:=1 to n do        begin read(val[i]); sum[i]:=val[i]; son[i,1]:=0; son[i,2]:=0; fa[i]:=0; rev[i]:=0; end;    readln(m);    for i:=1 to m do        begin            read(cha,ch,ch,ch,ch,ch);            case cha of            'b':begin readln(a,b); work1(a,b); end;            'p':begin readln(ch,ch,a,b); work2(a,b); end;            'e':begin readln(ch,ch,ch,a,b); work3(a,b); end;            end;        end;end.