bzoj 2748 DP

　　比较裸的背包，w[i][j]代表到第I个操作的时候音量j能不能达到，然后转移就行了。

　

/**************************************************************
    Problem: 2748
    User: BLADEVIL
    Language: Pascal
    Result: Accepted
    Time:12 ms
    Memory:284 kb
****************************************************************/
 
//By BLADEVIL
var
    n, s, h                     :longint;
    i, j                        :longint;
    v                           :array[0..60] of longint;
    w                           :array[0..60,0..1000] of boolean;
     
begin
    read(n,s,h);
    for i:=1 to n do read(v[i]);
     
    fillchar(w,sizeof(w),false);
    w[0][s]:=true;
    for i:=1 to n do
        for j:=0 to h do
        begin
            if j-v[i]>=0 then w[i][j]:=w[i][j] or w[i-1][j-v[i]];
            if j+v[i]<=h then w[i][j]:=w[i][j] or w[i-1][j+v[i]];
        end;
    for i:=h downto 0 do if w[n][i] then break;
    if (i=0) and (not w[n][i]) then writeln(-1) else writeln(i);
end.