Shredding Company

You have just been put in charge of developing a new shredder for the Shredding Company. Although a "normal" shredder would just shred sheets of paper into little pieces so that the contents would become unreadable, this new shredder needs to have the following unusual basic characteristics. 
The shredder takes as input a target number and a sheet of paper with a number written on it. 
It shreds (or cuts) the sheet into pieces each of which has one or more digits on it. 
The sum of the numbers written on each piece is the closest possible number to the target number, without going over it. 
For example, suppose that the target number is 50, and the sheet of paper has the number 12346. The shredder would cut the sheet into four pieces, where one piece has 1, another has 2, the third has 34, and the fourth has 6. This is because their sum 43 (= 1 + 2 + 34 + 6) is closest to the target number 50 of all possible combinations without going over 50. For example, a combination where the pieces are 1, 23, 4, and 6 is not valid, because the sum of this combination 34 (= 1 + 23 + 4 + 6) is less than the above combination‘s 43. The combination of 12, 34, and 6 is not valid either, because 52 (= 12 + 34 + 6) is greater than the target number of 50.

There are also three special rules:

If the target number is the same as the number on the sheet of paper, then the paper is not cut. For example, if the target number is 100 and the number on the sheet of paper is also 100, then the paper is not cut. 
If it not possible to make any combination whose sum is less than or equal to the target number, then error is printed on a display. For example, if the target number is 1 and the number on the sheet of paper is 123, it is not possible to make any valid combination, as the combination with the smallest possible sum is 1, 2, 3. The sum for this combination is 6, which is greater than the target number, and thus error is printed. 
If there is more than one possible combination where the sum is closest to the target number without going over it, then rejected is printed on a display. For example, if the target number is 15, and the number on the sheet of paper is 111, then there are two possible combinations with the highest possible sum of 12: (a) 1 and 11 and (b) 11 and 1; thus rejected is printed. 
In order to develop such a shredder, you have decided to first make a simple program that would simulate the above characteristics and rules. Given two numbers, where the first is the target number and the second is the number on the sheet of paper to be shredded, you need to figure out how the shedder should "cut up" the second number.

50 12346
376 144139
927438 927438
18 3312
9 3142
25 1299
111 33333
103 862150
6 1104
0 0

43 1 2 34 6
283 144 139
927438 927438
18 3 3 12
error
21 1 2 9 9
rejected
103 86 2 15 0
rejected

题意：给一串数把他拆成若干份，使他们的和小于等于给定的goal，而且尽可能接近goal。

思路：dfs暴力枚举，注意可能不止6位。

代码：

#include <iostream>
#include <functional>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <string>
#include <map>
#include <stack>
#include <vector>
#include <set>
#include <queue>
#pragma comment (linker,"/STACK:102400000,102400000")
#define pi acos(-1.0)
#define eps 1e-6
#define lson rt<<1,l,mid
#define rson rt<<1|1,mid+1,r
#define FRE(i,a,b)  for(i = a; i <= b; i++)
#define FREE(i,a,b) for(i = a; i >= b; i--)
#define FRL(i,a,b)  for(i = a; i < b; i++)
#define FRLL(i,a,b) for(i = a; i > b; i--)
#define mem(t, v)   memset ((t) , v, sizeof(t))
#define sf(n)       scanf("%d", &n)
#define sff(a,b)    scanf("%d %d", &a, &b)
#define sfff(a,b,c) scanf("%d %d %d", &a, &b, &c)
#define pf          printf
#define DBG         pf("Hi\n")
typedef long long ll;
using namespace std;

#define INF 0x3f3f3f3f
#define mod 1000000009
const int maxn = 1005;
const int MAXN = 2005;
const int MAXM = 200010;
const int N = 1005;

char str[maxn];
int a[maxn],b[maxn];
int goal,len;
int Max;
vector<int>ans,vec;
vector<vector<int> >out;

void dfs(int pos,int sum)
{
    if (sum+b[len]-b[pos-1]>goal) return ;  //当前的sum加上剩下全部单个数之和比goal还大那肯定不行
    if (pos==len+1&&sum<=goal)
    {
        if (Max<=sum)
        {
            ans.push_back(sum);
            if (out.size()!=0)
                out.pop_back();
            out.push_back(vec);
            Max=sum;
        }
        return ;
    }
    for (int i=pos;i<=len;i++)  //枚举终点
    {
        int s=0;
        for (int j=pos;j<=i;j++)
        {
            s=s*10+a[j];
        }
        vec.push_back(s);
        dfs(i+1,sum+s);
        vec.pop_back();
    }
    return ;
}

int main()
{
#ifndef ONLINE_JUDGE
    freopen("C:/Users/lyf/Desktop/IN.txt","r",stdin);
#endif
    int i,j;
    while (scanf("%d %s",&goal,str+1))
    {
        if (goal==0&&str[1]=='0') break;
        int x=0;
        memset(b,0,sizeof(b));
        len=strlen(str+1);
        for (i=1;i<=len;i++)
        {
            a[i]=str[i]-'0';
            x=x*10+str[i]-'0';
            b[i]=b[i-1]+a[i];
        }
        if (x==goal){
            printf("%d %d\n",goal,goal);
            continue;
        }
        if (b[len]>goal){
            printf("error\n");
            continue;
        }
        Max=0;
        out.clear();
        ans.clear();
        vec.clear();
        dfs(1,0);
        int sz=ans.size();
        if (ans[sz-1]==ans[sz-2]) printf("rejected\n");
        else
        {
            printf("%d",ans[sz-1]);
            for (i=0;i<out[0].size();i++)
                printf(" %d",out[0][i]);
            printf("\n");
        }
    }
    return 0;
}