P1120-小木棍 ［数据加强版］

 1 #include <bits/stdc++.h>
 2 #define _for(i,a,b) for(int i = (a);i < b;i ++)
 3 #define _rep(i,a,b) for(int i = (a);i > b;i --)
 4 #define INF 0x3f3f3f3f
 5 typedef long long ll;
 6 using namespace std;
 7 inline ll read()
 8 {
 9     ll ans = 0;
10     char ch = getchar(), last = ‘ ‘;
11     while(!isdigit(ch)) last = ch, ch = getchar();
12     while(isdigit(ch)) ans = (ans << 1) + (ans << 3) + ch - ‘0‘, ch = getchar();
13     if(last == ‘-‘) ans = -ans;
14     return ans;
15 }
16 inline void write(ll x)
17 {
18     if(x < 0) x = -x, putchar(‘-‘);
19     if(x >= 10) write(x / 10);
20     putchar(x % 10 + ‘0‘);
21 }
22 int N;
23 int a[66],Next[66],vis[66];
24 int aend = 0;
25 int sum = 0;
26 int num;
27 bool dfs(int k,int la,int re)
28 {
29     if(!re)
30     {
31         if(k==num) return true;
32 
33         _for(i,1,aend+1)
34         if(!vis[i])
35         {
36             vis[i] = 1;
37             if(dfs(k+1,i,(sum/num)-a[i])) return true;
38             else
39             {
40                 vis[i] = 0;
41                 return false;
42             }
43         }
44         return false;
45     }
46 
47     int t = lower_bound(a+la,a+aend+1,re,greater<int>())-a;
48     _for(i,t,aend+1)
49         if(!vis[i])
50         {
51             vis[i] = 1;
52             if(dfs(k,i,re-a[i])) return true;
53             vis[i] = 0;
54 
55             if(re==a[i] || re==sum/num)    return false;
56             i = Next[i];
57             if(i==aend) return false;
58         }
59     return false;
60 }
61 int main()
62 {
63     N = read();
64     int t;
65     _for(i,1,N+1)
66     {
67         t = read();
68         if(t>50)
69             continue;
70         a[++aend] = t;
71         sum += a[aend];
72     }
73     sort(a+1,a+aend+1,greater<int>());
74 
75     Next[aend] = aend;
76     _rep(i,aend-1,0)
77     {
78         if(a[i]==a[i+1]) Next[i] = Next[i+1];
79         else Next[i] = i;
80     }
81 
82     memset(vis,0,sizeof(vis));
83     int rnt = sum;
84     _for(len,a[1],sum/2+1)
85     {
86         if(sum % len != 0) continue;
87         num = sum/len;
88         vis[1] = 1;
89         if(dfs(1,1,len-a[1]))
90         {
91             rnt = len;
92             break;
93         }
94         vis[1]= 0;
95     }
96     write(rnt);
97     return 0;
98 }