Splatter Painting

最新推荐文章于 2020-09-10 16:41:00 发布

原创最新推荐文章于 2020-09-10 16:41:00 发布 · 388 阅读

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本文介绍了一种解决图染色问题的方法，通过反向操作避免重复染色，并使用标记记录节点染色范围来提高效率。

http://agc012.contest.atcoder.jp/submissions/1414860

Problem Statement
Squid loves painting vertices in graphs.
There is a simple undirected graph consisting of N vertices numbered 1 through N, and M edges. Initially, all the vertices are painted in color 0. The i-th edge bidirectionally connects two vertices ai and bi. The length of every edge is 1.
Squid performed Q operations on this graph. In the i-th operation, he repaints all the vertices within a distance of di from vertex vi, in color ci.
Find the color of each vertex after the Q operations.

自行翻译
大致是有n个点m条边 q个操作
每个操作是将点u及到它距离在d以内的点染上c

我们可以从后向前找这样就不会重复染色
另外我们可以对每个点向外的范围进行记录，扫描时如果剩下的范围小于点上标记的范围
就不要扫下去了
（manacher？？）

var i,j,k,l,m,n,q,w,x,y,t:longint;
    st,ed,first,next,d,v,color,fw,c:array[1..200000] of longint;
    b:array[1..200000]of boolean;
procedure ad(p,o:longint);
begin
    t:=t+1;  ed[t]:=o; next[t]:=first[p];first[p]:=t;
end;
procedure dfs(p,o,cl:longint);
var i,j:longint;
begin
    if fw[p]>=o then exit;
    i:=first[p]; fw[p]:=o;  b[p]:=true;
    if color[p]=0 then color[p]:=cl;
    while (i>=1) do begin
        if b[ed[i]]=false then
               dfs(ed[i],o-1,cl);
        i:=next[i];
    end;
   b[p]:=false;
end;
begin
    readln(n,m);
    for i:=1 to m do first[i]:=-1;
    fillchar(fw,sizeof(fw),255);
    for i:=1 to m do begin readln(x,y); ad(x,y);ad(y,x); end;
    readln(q);
    for i:=1 to q do readln(v[i],d[i],c[i]);
    for i:=q downto 1 do begin dfs(v[i],d[i],c[i]); end;
    for i:=1 to n do writeln(color[i]);
end.

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