Simonepascal做21点或者24点游戏
的有关信息介绍如下：
【算法分析】 计算24点（或21点）主要应用四种运算．开始状态有四个操作数，一个运算符对应两个操作数， 所以一开始选择两个操作数分别对四个操作符进行循环检测， 每一次运算后产生了新的数，两个数运算变成一个数，整体是少了一个操作数，所以四个数最终是三次运算。由于操作的层数比较少(只有三层)， 所以可以用回溯的算法来进行检测，当找到一个解时便结束查找。如果所有的情况都找过后仍然没有，则输出无解的信息。rogram point24(input,output); type arr=array [1..4] of integer; var i,result,n,len:integer; d:arr; r:array [1..3,1..4] of integer; infile,outfile:text; procedure print; var i,j:integer; begin assign(outfile,'point24.out');rewrite(outfile); for i:=1 to 3 do begin for j:=1 to 3 do if j<>2 then write(outfile,r[i,j]) else case r[i,j] of 1:write(outfile,'+'); 2:write(outfile,'-'); 3:write(outfile,'*'); 4:write(outfile,'/') end; end; close(outfile); end; procedure try(k:integer;d:arr); var a,b,i,j,l,t:integer; e:arr; begin if k=1 then if d[1]=24 then begin print; halt end else else begin for i:=1 to k-1 do for j:=i+1 to k do begin a:=d[i]; b:=d[j]; if ai) and (l<>j) then begin t:=t+1;e[t]:=d[l] end; r[5-k,1]:=a; r[5-k,3]:=b; r[5-k,4]:=-1; for l:=1 to 4 do begin case l of 1:r[5-k,4]:=a+b; 2:r[5-k,4]:=a-b; 3:r[5-k,4]:=a*b; 4:if b<>0 then if a mod b=0 then r[5-k,4]:=a div b end; r[5-k,2]:=l; if r[5-k,4]<>-1 then begin e[t+1]:=r[5-k,4]; try(k-1,e) end end end end;end;begin assign(infile,'point24.in');reset(infile); for i:=1 to 4 do read(infile,d[i]); close(infile); try(4,d); assign(outfile,'point24.out'); rewrite(outfile); writeln(outfile,'No answer!'); close(outfile);end.
