1 #include <stdio.h>
2 #include <stdlib.h>
3
4
5 int n; //Number of sticks
6
7
8 bool dfs( int* stick, bool *vist, int len, int InitLen, int s, int num) // len: sum of current sticks; Initlen: target initial length
9 // s: the looking start of sticks; num: number of sticks used
10 {
11 if (num == n)
12 return true;
13 int sample = -1; //record the current stick's length
14
15 for (int i = s; i < n; i++)
16 {
17 if (vist[i] || stick[i] == sample) // Prune 3, sticks with same sticks can be used only once
18 continue;
19
20 vist[i] = true;
21
22 if ( len + stick[i] < InitLen)
23 {
24 if (dfs(stick, vist, len+stick[i], InitLen, i, num+1))
25 return true;
26 else
27 sample = stick[i];
28 }
29 else if (len + stick[i] == InitLen)
30 {
31 if (dfs(stick, vist, 0 , InitLen, 0, num+1))
32 return true;
33 else
34 sample = stick[i];
35 }
36 vist[i] = false;
37 if (len == 0) // Prune 4, the failed first sticks returns
38 break;
39 }
40
41 return false;
42
43 }
44
45
46
47
48
49
50 int cmp(const void* a, const void *b)
51 {
52 return *(int*)b - *(int*)a;
53 }
54
55
56 int main(void)
57 {
58 while( (scanf("%d", &n)) && n)
59 {
60
61 int* stick = (int*) malloc(sizeof(int) * n);
62 bool* vist = (bool*) malloc(sizeof(bool) * n);
63 int sumlen = 0;
64
65 for(int i = 0; i < n; i++)
66 {
67 scanf("%d", &(stick[i]));
68 sumlen += stick[i];
69 vist[i]=false;
70 }
71
72 qsort(stick,n,sizeof(stick),cmp);
73
74 int maxlen = stick[0]; //Biggest stick has number 1
75
76 bool flag=false; //What is it?
77
78 // Prune 1, the shortest length must lie in [maxlen, sumlen - InitLen]
79 for (int InitLen = maxlen; InitLen <= sumlen - InitLen; InitLen++)
80 { //Prune 2, the Initlen must be the factor of number sumlen
81 if ( !(sumlen % InitLen) && dfs(stick, vist, 0, InitLen, 0, 0) )
82 {
83 printf("%d\n", InitLen);
84 flag=true;
85 break;
86 }
87 }
88
89 if (!flag)
90 printf("%d\n", sumlen);
91
92 free(stick);
93 stick = NULL;
94 free(vist);
95 vist = NULL;
96 }
97 return 0;
98 }
