动态规划
//为了方便边界跨越，人的数组下标从0开始。a[i,j]编号为i的人表示j次传球以后有多少种方式获得球。var n,m,i,j:longint; a:array[0..30,0..30] of longint;begin assign(input,'ballg.in'); reset(input); assign(output,'ballg.out'); rewrite(output); readln(n,m); for i:=1 to n-1 do a[i,0]:=0; a[0,0]:=1;//球还没有开始传，在0号，即小蛮手中 for j:=1 to m do//表示第几次传球 for i:=0 to n do a[i,j]:=a[(i+1) mod n,j-1]+a[(i-1+n) mod n,j-1];//每个人只能从上一个或下一个人手中拿到球 writeln(a[0][m]); close(input); close(output);end.
var n,m:longint; ans:int64;procedure find(i,j:integer);begin if (i=m) then begin if j=1 then ans:=ans+1; exit; end; find(i+1,j mod n+1); if j=1 then find(i+1,n) else find(i+1,j-1);end;begin readln(n,m); if (n mod 2=0) and (m mod 2=1) then begin writeln('0'); halt; end; find(0,1); writeln(ans);end.
var n,m,c,i:longint; ans:int64; next,pre:array[1..1000] of longint;procedure DFS(j:integer);begin if(c=m) then begin if j=1 then ans:=ans+1; exit; end; inc(c); DFS(next[j]); dec(c); inc(c); DFS(pre[j]); dec(c);end;begin readln(n,m); if (n mod 2=0) and (m mod 2=1) then begin writeln('0'); halt; end; for i:=1 to n-1 do next[i]:=i+1; next[n]:=1; for i:=2 to n do pre[i]:=i-1; pre[1]:=n; c:=0; DFS(1); writeln(ans);end.
var n,m,i:longint; ans:int64; next,pre:array[1..1000] of longint;procedure DFS(i,j:integer);begin if(i=m) then begin if j=1 then ans:=ans+1; exit; end; DFS(i+1,next[j]); DFS(i+1,pre[j]);end;begin readln(n,m); if (n mod 2=0) and (m mod 2=1) then begin writeln('0'); halt; end; for i:=1 to n-1 do next[i]:=i+1; next[n]:=1; for i:=2 to n do pre[i]:=i-1; pre[1]:=n; DFS(0,1); writeln(ans);end.