POJ1787

题意:现在有4种面值的货币,给出每种货币的数量,求是否能用这4种货币组成总额为P.若存在,则输出该方案.

分析:多重背包,数组标记,记录路径.

code:

type  rec=record
      fa,tot:longint;
end;
var   a:array[1..4] of longint=(1,5,10,25);
      c,ans:array[1..4] of longint;
      f:array[0..10001] of boolean;
      count:array[0..10001] of longint;
      path:array[0..10001] of rec;
      i,j,m,cur:longint;

      function sum:longint;
      begin
            sum:=m+c[1]+c[2]+c[3]+c[4];
      end;

      procedure init;
      begin
            read(m);
            for i:=1 to 4 do read(c[i]);
            if sum=0 then halt;
            readln;
      end;

      procedure work;
      begin
            fillchar(f,sizeof(f),0);
            fillchar(path,sizeof(path),0);
            f[0]:=true;
            for i:=1 to 4 do
            begin
                  fillchar(count,sizeof(count),0);
                  for j:=a[i] to m do
                  if (not f[j] or (path[j-a[i]].tot+1>path[j].tot))
                     and(f[j-a[i]])and(count[j-a[i]]<c[i]) then
                  begin
                        f[j]:=true;
                        path[j].tot:=path[j-a[i]].tot+1;
                        path[j].fa:=j-a[i];
                        count[j]:=count[j-a[i]]+1;
                  end;
            end;
      end;

      procedure print;
      begin
            if f[m]=false then
              writeln('Charlie cannot buy coffee.')
            else
            begin
                  fillchar(ans,sizeof(ans),0);
                  cur:=m;
                  while cur<>0 do
                  begin
                        case cur-path[cur].fa of
                        1:inc(ans[1]);
                        5:inc(ans[2]);
                        10:inc(ans[3]);
                        25:inc(ans[4]);
                        end;
                        cur:=path[cur].fa;
                  end;
                  writeln('Throw in ',
                          ans[1],' cents, ',
                          ans[2],' nickels, ',
                          ans[3],' dimes, and ',
                          ans[4],' quarters.');
            end;
      end;
begin
      while not eof do
      begin
            init;
            work;
            print;
      end;
end.