HDU_1455_dfs

http://acm.hdu.edu.cn/showproblem.php?pid=1455

int dfs(int all,int sum,int now)，all代表剩余总长，sum，代表每段长，now代表当前拼接的长度。

if(a[i]+now == sum || now == 0) return 0;
while(a[i+1] == a[i]) i++;

这两句话剪枝很重要。

#include<iostream>
#include<string>
#include<cstring>
#include<algorithm>
using namespace std;

int a[],used[],n;

bool cmp(int a,int b)
{
    return a>b;
}

int dfs(int all,int sum,int now)
{
    if(all ==  && now == sum)  return ;
    if(now == sum)  now = ;
    for(int i = ;i <= n;i++)
    {
        if(used[i] || a[i]+now > sum)   continue;
        used[i] = ;
        if(dfs(all-a[i],sum,now+a[i]))  return ;
        used[i] = ;
        if(a[i]+now == sum || now == ) return ;
        while(a[i+] == a[i])   i++;
    }
    return ;
}
int main()
{
    while(cin >> n && n)
    {
        int sum = ;
        for(int i = ;i <= n;i++)
        {
            cin >> a[i];
            sum += a[i];
        }
        sort(a+,a+n+,cmp);
        for(int i = a[];i <= sum;i++)
        {
            if(sum%i)   continue;
            memset(used,,sizeof(used));
            if(dfs(sum,i,))
            {
                cout << i << endl;
                break;
            }
        }
    }
    return ;
}