[BZOJ1621][Usaco2008 Open]Roads Around The Farm分岔路口

传送门

http://www.lydsy.com/JudgeOnline/problem.php?id=1621

题目大意

每次n个物品分为x和x+k,直到不能按照上述分法分开,询问有多少堆

题解

小学数学….

n+k2和n−k2\frac{n+k}{2}和\frac{n-k}{2}

当(n+k)mod 2<>0或(n−k)mod 2<>0或n<=k时当(n+k)mod\ \ 2<>0或(n-k)mod\ \ 2<>0或n<=k时不能再分

DFS

var
i,j,k:longint;
n,ans:longint;
procedure f(a:longint);
begin
if (a+k)mod 2<>0 then begin inc(ans); exit; end;
if a<=k then begin inc(ans); exit; end;
if (a-k)mod 2<>0 then begin inc(ans); exit; end;
f((a+k)div 2); f((a-k)div 2);
end;

begin
readln(n,k);
ans:=0;
f(n);
writeln(ans);
end.