1907: 树的路径覆盖

1907: 树的路径覆盖

Time Limit: 5 Sec  Memory Limit: 259 MB
Submit: 506  Solved: 219
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Description

Input

Output

Sample Input

1
7
1 2
2 3
2 4
4 6
5 6
6 7

Sample Output

3

HINT

Source

Play with Tree By Amber

 

题解：贪心题么么哒，直接DFS一遍就好啦

/**************************************************************
    Problem: 1907
    User: HansBug
    Language: Pascal
    Result: Accepted
    Time:392 ms
    Memory:3480 kb
****************************************************************/
 
type
    point=^node;
    node=record
               g:longint;
               next:point;
    end;
var
   i,j,k,l,m,n,tot,t:longint;
   a:array[0..100000] of point;
   b:array[0..100000] of longint;
   c:array[0..100000] of boolean;
procedure add(x,y:longint);
          var p:point;
          begin
               new(p);p^.g:=y;p^.next:=a[x];a[x]:=p;
          end;
procedure dfs(y,x:longint);
          var p:point;tot:longint;
          begin
               b[x]:=1;tot:=0;p:=a[x];
               while p<>nil do
                     begin
                          if p^.g<>y then
                             begin
                                  dfs(x,p^.g);
                                  inc(b[x],b[p^.g]);
                                  if not(c[p^.g]) then inc(tot);
                             end;
                          p:=p^.next;
                     end;
               if tot>=2 then
                  begin
                       dec(b[x],2);
                       c[x]:=true;
                  end
               else if tot=1 then dec(b[x]);
          end;
begin
     readln(t);
     while t>0 do
           begin
                readln(n);
                fillchar(b,sizeof(b),0);
                fillchar(c,sizeof(c),false);
                for i:=1 to n do a[i]:=nil;
                for i:=1 to n-1 do
                    begin
                         readln(j,k);
                         add(j,k);add(k,j);
                    end;
                dfs(0,1);dec(t);
                writeln(b[1]);
           end;
end.