【HDOJ】1455 Sticks
DFS。搜索以棍数为条件循环搜索较好，这样不会超时。
1 #include <stdio.h> 2 #include <string.h> 3 #include <stdlib.h> 4 5 #define true 1 6 #define false 0 7 #define MAXN 70 8 9 int alen; 10 int parts[MAXN]; 11 char visit[MAXN]; 12 int n, m; 13 14 int dfs(int beg, int cnt, int len) { 15 int i; 16 17 if (len == 0) { 18 ++cnt; 19 if (cnt+1 == m) 20 return true; 21 22 for (i=0; i<n; ++i) 23 if ( !visit[i] ) 24 break; 25 26 visit[i] = 1; 27 if ( dfs(i+1, cnt, alen-parts[i]) ) 28 return true; 29 visit[i] = 0; 30 31 return false; 32 } 33 34 for (i=beg; i<n; ++i) { 35 if (visit[i] || parts[i]>len) 36 continue; 37 if (i && parts[i]==parts[i-1] && !visit[i-1]) 38 continue; 39 visit[i] = 1; 40 if ( dfs(i+1, cnt, len-parts[i]) ) 41 return true; 42 visit[i] = 0; 43 } 44 45 return false; 46 } 47 48 int comp(const void *a, const void *b) { 49 return *(int *)b - *(int *)a; 50 } 51 52 int main() { 53 int sum; 54 int i; 55 56 while (scanf("%d", &n)!=EOF && n) { 57 sum = 0; 58 for (i=0; i<n; ++i) { 59 scanf("%d", &parts[i]); 60 sum += parts[i]; 61 } 62 qsort(parts, n, sizeof(int), comp); 63 m = n+1; 64 while (m > 1) { 65 --m; 66 if (sum%m) 67 continue; 68 alen = sum/m; 69 if (parts[0] > alen) 70 continue; 71 memset(visit, 0, sizeof(visit)); 72 if ( dfs(0, 0, alen) ) 73 break; 74 } 75 printf("%d\n", alen); 76 } 77 78 return 0; 79 }
