题解

244 条题解

  • 0
    @ 2013-05-26 20:03:05

    终于秒了 没看到Impossible一直输出0 卡了好久55

    VijosEx via JudgeDaemon2/13.5.1.0 via libjudge
    编译成功

    测试数据 #0: Accepted, time = 0 ms, mem = 476 KiB, score = 10
    测试数据 #1: Accepted, time = 0 ms, mem = 476 KiB, score = 10
    测试数据 #2: Accepted, time = 0 ms, mem = 476 KiB, score = 10
    测试数据 #3: Accepted, time = 0 ms, mem = 472 KiB, score = 10
    测试数据 #4: Accepted, time = 0 ms, mem = 476 KiB, score = 10
    测试数据 #5: Accepted, time = 0 ms, mem = 476 KiB, score = 10
    测试数据 #6: Accepted, time = 0 ms, mem = 476 KiB, score = 10
    测试数据 #7: Accepted, time = 0 ms, mem = 472 KiB, score = 10
    测试数据 #8: Accepted, time = 0 ms, mem = 476 KiB, score = 10
    测试数据 #9: Accepted, time = 0 ms, mem = 472 KiB, score = 10
    Accepted, time = 0 ms, mem = 476 KiB, score = 100

    #include <iostream>
    #include <algorithm>
    #include <cstring>

    using namespace std;

    #define MAXN 100
    #define MAXS 1001

    int k=0;
    int f[MAXS][2];
    int n;
    int a[MAXN];
    int sum=0;

    int main(){
    memset(f,0,sizeof(f));
    cin>>n;
    for (int i=0;i<n;i++){
    cin>>a[i];
    sum+=a[i];
    }
    f[0][0]=1;
    sum/=2;
    for (int i=0;i<n;i++){
    for (int j=0;j<=sum;j++){
    if (f[j][k]){
    f[j][k^1]=max(f[j][k^1],f[j][k]);
    if (j>=a[i]) f[j-a[i]][k^1]=max(f[j-a[i]][k^1],f[j][k]+a[i]);
    else f[a[i]-j][k^1]=max(f[a[i]-j][k^1],f[j][k]+j);
    if (j+a[i]<=sum) f[j+a[i]][k^1]=max(f[j+a[i]][k^1],f[j][k]);
    }
    }
    k^=1;
    }
    if (f[0][k]-1) cout<<f[0][k]-1<<endl; else cout<<"Impossible"<<endl;
    return 0;
    }

  • 0
    @ 2013-03-30 20:55:40
  • 0
    @ 2013-02-24 14:17:26

    AC10纪念,刚刚从tyvj的崩溃阴影中走出来…………
    测试数据 #0: Accepted, time = 0 ms, mem = 1572 KiB, score = 10

    测试数据 #1: Accepted, time = 15 ms, mem = 1568 KiB, score = 10

    测试数据 #2: Accepted, time = 7 ms, mem = 1568 KiB, score = 10

    测试数据 #3: Accepted, time = 15 ms, mem = 1576 KiB, score = 10

    测试数据 #4: Accepted, time = 15 ms, mem = 1568 KiB, score = 10

    测试数据 #5: Accepted, time = 7 ms, mem = 1568 KiB, score = 10

    测试数据 #6: Accepted, time = 15 ms, mem = 1576 KiB, score = 10

    测试数据 #7: Accepted, time = 0 ms, mem = 1572 KiB, score = 10

    测试数据 #8: Accepted, time = 15 ms, mem = 1576 KiB, score = 10

    测试数据 #9: Accepted, time = 31 ms, mem = 1576 KiB, score = 10

    Summary: Accepted, time = 120 ms, mem = 1576 KiB, score = 100

    代码
    program P1037;
    var
    i,j,sum,n:longint;
    dp:array[0..100,0..2000]of longint;
    h:array[1..100]of longint;
    function max(a,b:longint):longint;
    begin
    if a>b then
    max:=a
    else max:=b;
    end;
    procedure print;
    begin
    if dp[n,0]>0 then
    writeln(dp[n,0])
    else writeln('Impossible');
    end;
    begin
    readln(n);
    for i:=1 to n do
    begin
    read(h[i]);
    inc(sum,h[i]);
    end;
    for i:=0 to n do
    for j:=0 to sum do
    dp[i,j]:=-maxint;
    dp[0,0]:=0;
    for i:=1 to n do
    for j:=sum downto 0 do
    begin
    if j>h[i] then
    dp[i,j]:=max(max(dp[i-1,j],dp[i-1,j-h[i]]+h[i]),dp[i-1,j+h[i]]);
    if h[i]>=j then
    dp[i,j]:=max(max(dp[i-1,j],dp[i-1,h[i]-j]+j),dp[i-1,j+h[i]]);
    end;
    print;
    end.

  • 0
    @ 2009-11-08 15:26:50

    搞了好久,终于把方程式弄懂了。

    看来,写方程式时,阶段与状态的选取还是很重要的。

  • 0
    @ 2009-11-06 11:06:21

    var

    f:array[-2000..2000,-2000..2000]of boolean;

    a:array[1..2000]of longint;

    n,m,i,j,k,l,sum,ans:longint;

    begin

    readln(n);

    f[0,0]:=true;

    for i:=1 to n do

    begin

    read(a[i]);

    inc(ans,a[i]);

    end;

    for l:=1 to n do

    begin

    inc(sum,a[l]);

    if sum>ans div 2 then sum:=ans div 2;//小优化

    for i:=sum downto 0 do

    for j:=sum downto 0 do

    f:=for f[i,j-a[l]]or f[i-a[l],j];

    end;

    for i:=sum downto 1 do

    if f

    then begin

    write(i);

    halt;

    end;

    write('Impossible');

    end.

  • 0
    @ 2009-11-06 10:12:03

    编译通过...

    ├ 测试数据 01:答案正确... 0ms

    ├ 测试数据 02:答案正确... 0ms

    ├ 测试数据 03:答案正确... 0ms

    ├ 测试数据 04:答案正确... 446ms

    ├ 测试数据 05:答案正确... 0ms

    ├ 测试数据 06:答案正确... 430ms

    ├ 测试数据 07:答案正确... 805ms

    ├ 测试数据 08:运行超时...

    ├ 测试数据 09:运行超时...

    ├ 测试数据 10:运行超时...

  • 0
    @ 2009-11-04 16:45:25

    var

    f:array[0..2000,0..2000] of boolean;

    n,i,j,sum,x,k:longint;

    begin

    readln(n);

    f[0,0]:=true;

    for i:=1 to n do

    begin

    read(x);

    for j:=sum downto 0 do

    for k:=sum downto 0 do

    if f[j,k] then

    begin

    f[j+x,k]:=true;

    f[j,k+x]:=true;

    end;

    sum:=sum+x;

    end;

    for i:=sum downto 1 do

    if f then

    begin

    writeln(i);

    halt;

    end;

    writeln('Impossible');

    end.

  • 0
    @ 2009-11-03 14:33:09

    设f表示前i块水晶,两塔高度差为j时较高的那个塔的高度。

    DP方程:

    f=max{f,f,f+j} (j=h[i])

    解析:

    f 表示不放第i块水晶;

    f 表示第i块水晶放到了较矮的那个塔上,而且矮塔仍然为矮塔,填补了高度差;

    f+j 表示第i块水晶放到了较矮的那个塔上,但是矮塔变成了高塔;

    f+h[i] 表示第i块水晶放到了较高的塔上,增加了高度差;

    边界条件:

    如果刚开始的f值都为0的话,调试的时候会发现,有许多不合逻辑的答案,例如:h[1]=1,f[1,2]也会算出值为1,但其实是无法用高度为1的水晶搭出高度差大于等于2的双塔的。

    所以要把所先把所有的f赋成-maxlongint,然后f[0,0]:=0。

    程序代码:

    var

    f:array[0..100,0..2000]of integer;

    n,sum,i,j,k:integer;

    h:array[1..100]of integer;

    function max(x,y,z:integer):integer;

    begin

    max:=x;

    if max

  • 0
    @ 2009-11-02 20:47:06

    var

    b,c,d,m,n,i,j,sum:longint;

    a:array[0..200] of longint;

    f:array[0..200,0..20000] of longint;

    procedure init;

    begin

    read(m);

    sum:=0;

    for i:=1 to m do

    begin

    read(a[i]);

    sum:=sum+a[i];

    end;

    for i:= 0 to m do

    for j:=1 to sum do f:=-maxlongint;

    end;

    procedure main;

    begin

    f[0,0]:=0;

    for i:=1 to m do

    for j:=sum downto 0 do

    begin

    if f

  • 0
    @ 2009-11-02 12:56:55

    初始值弄错了,只得20分

  • 0
    @ 2009-11-01 18:04:42

    编译通过...

    ├ 测试数据 01:答案正确... 0ms

    ├ 测试数据 02:答案正确... 0ms

    ├ 测试数据 03:答案正确... 0ms

    ├ 测试数据 04:答案正确... 0ms

    ├ 测试数据 05:答案正确... 0ms

    ├ 测试数据 06:答案正确... 0ms

    ├ 测试数据 07:答案正确... 0ms

    ├ 测试数据 08:答案正确... 0ms

    ├ 测试数据 09:答案正确... 0ms

    ├ 测试数据 10:答案正确... 0ms

    ---|---|---|---|---|---|---|---|-

    Accepted 有效得分:100 有效耗时:0ms

    program ex;

    var i,j,n,sum:longint;

    h:array[1..100]of longint;

    f:array[0..100,0..2000]of longint;

    procedure init;

    var i,j:longint;

    begin

    readln(n);

    for i:=1 to n do read(h[i]);

    end;

    function max(a,b:longint):longint;

    begin

    if a>b then exit(a) else exit(b);

    end;

    procedure dp;

    var i,j:longint;

    begin

    filldword(f,sizeof(f)div 4,-maxlongint);

    f[0,0]:=0;

    for i:=1 to n do

    begin

    inc(sum,h[i]);

    for j:=0 to sum do

    begin

    if j>=h[i] then

    f:=max(f,max(f,f+h[i]));

    if h[i]>=j then

    f:=max(f,max(f,f+j));

    end;

    end;

    end;

    begin

    init;

    dp;

    if f[n,0]0 then writeln(f[n,0]) else writeln('Impossible');

    end.

  • 0
    @ 2009-10-31 21:03:27

    想快点通过的时候Vijos Easy几次都不来,只好优化

    等优化完想看在标准评测机上效率连着3次Easy

    在现在正常评测机为主流的情况下:1.快排2.还是分小塔大塔好,虽然就快100MS,也有效果,然后再按照下面题解做

  • 0
    @ 2009-10-30 21:38:51

    var

    b:array [0..2000,0..2000] of boolean;

    n,m,i,j,k,l,g:longint;

    begin

    fillchar(b,sizeof(b),false);

    readln(n);

    l:=0;

    b[0,0]:=true;

    for i:=1 to n do

    begin

    read(g);

    for j:=l downto 0 do

    for k:=l downto 0 do

    if b[j,k] then begin b[j+g,k]:=true;b[j,k+g]:=true;end;

    l:=l+g;

    end;

    for j:=l downto 1 do

    if b[j,j] then begin writeln(j);halt;end;

    writeln('Impossible');

    end.

  • 0
    @ 2009-10-29 20:21:24

    暴力

    Sunny 80分

    Easy AC

    人品啊!!

    ---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|

    广东实验中学观光团到此一游

  • 0
    @ 2009-10-26 17:36:14

    今天神奇ac~~~!!!!

  • 0
    @ 2009-10-25 11:19:46

    DP做法:

    f表示拿i个水晶搭出高低差为j的时候,较低的塔高;

    f:=f; //第i块水晶不参与搭建时,还是搭出了差为j的两座塔,用了前i-1块水晶;

    f:=f; // 第i块水晶参与搭建,加在较高的一座塔上,当j>=a[i]时,两座塔的高度差由j-a[i]变成了j,较低的塔的高度还是f;

    f:=f+a[i]; //当第i块水晶加在较低的一座塔上时,有两种情况,要么较低的塔加高后还是没有较高的塔高,则高度差减少了a[i],低塔的高度增加了a[i];

    f:=f+a[i]-j;//要么较低的塔加高后比较高的塔高一些,j

  • 0
    @ 2009-10-24 20:34:14

    f(i>=j)表示高度为i,j的双塔能否构成。

    if f then

    begin

    f:=true;

    if j+a

  • 0
    @ 2009-10-24 15:45:08

    这题用正推做更值

  • 0
    @ 2009-10-22 11:40:21

    sunny显示我超时4个点 可现在居然显示我AC了

    编译通过...

    ├ 测试数据 01:答案正确... 0ms

    ├ 测试数据 02:答案正确... 0ms

    ├ 测试数据 03:答案正确... 0ms

    ├ 测试数据 04:答案正确... 431ms

    ├ 测试数据 05:答案正确... 0ms

    ├ 测试数据 06:答案正确... 588ms

    ├ 测试数据 07:运行超时...

    ├ 测试数据 08:运行超时...

    ├ 测试数据 09:运行超时...

    ├ 测试数据 10:运行超时...

    ---|---|---|---|---|---|---|---|-

    Unaccepted 有效得分:60 有效耗时:1019ms

    var

    n,i,j,k,x,ji:longint;

    f:array[0..2000,0..2000]of boolean;

    begin

    readln(n);

    fillchar(f,sizeof(f),0);

    ji:=0;

    f[0,0]:=true;

    for i:=1 to n do

    begin

    read(x);

    for j:=ji downto 0 do

    for k:=ji downto 0 do

    if f[j,k] then

    begin

    f[j+x,k]:=true;

    f[j,k+x]:=true;

    end;

    ji:=ji+x;

    end;

    for i:=ji downto 0 do

    if f then break;

    if i=0 then writeln('Impossible') else writeln(i);

    end.

  • 0
    @ 2009-10-17 20:14:47

    这题已经刷掉两点通过率了- -

    可是impossible那个点就是过不去..

    我都想cheat了- -

    然后有没有人能告诉我..

    为什么不可以加 if (j+a[i]

信息

ID
1037
难度
6
分类
动态规划 | 背包 点击显示
标签
(无)
递交数
10535
已通过
2737
通过率
26%
被复制
16
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