poj1011 Sticks
搜索题。
枚举最小长度进行搜索。但是考虑到先进A/先进B是等效的，我们规定只能从i往i + 1进同一根木棒。
sort是最原始的剪枝手段。然后还有，等长木棒的等效性，0长度时任一木棒的等效性。
这样我们就0msAC了
搜索的时候我把i写成了k直接爆0
1 #include <cstdio> 2 #include <algorithm> 3 using std::sort; 4 const int N = 100; 5 6 int n, a[N], tot, len, cnt; 7 bool vis[N]; 8 9 inline bool cmp(const int &a, const int &b) { 10 return a > b; 11 } 12 13 bool DFS(int k, int now, int l) { 14 //printf("DFS: %d %d %d \n", k, now, l); 15 if(now == cnt + 1) { 16 return 1; 17 } 18 int last = -1; 19 for(int i = k; i <= n; i++) { 20 if(vis[i] || a[i] == last) continue; 21 //printf("%d \n", i); 22 last = a[i]; 23 if(a[i] + l < len) { 24 vis[i] = 1; 25 bool t = DFS(i + 1, now, l + a[i]); 26 vis[i] = 0; 27 if(t) return 1; 28 if(!l) { 29 return 0; 30 } 31 } 32 else if(a[i] + l == len) { 33 vis[i] = 1; 34 bool t = DFS(1, now + 1, 0); 35 vis[i] = 0; 36 if(t) return 1; 37 if(!l) { 38 return 0; 39 } 40 } 41 } 42 return 0; 43 } 44 45 int main() { 46 while(scanf("%d", &n) && n) { 47 tot = 0; 48 for(int i = 1; i <= n; i++) { 49 scanf("%d", &a[i]); 50 tot += a[i]; 51 } 52 sort(a + 1, a + n + 1, cmp); 53 /*for(int i = 1; i <= n; i++) { 54 printf("%d ", a[i]); 55 } 56 puts("");*/ 57 for(int i = a[1]; i <= tot; i++) { 58 if(tot % i == 0) { 59 len = i; 60 cnt = tot / i; 61 //printf("i = %d len = %d cnt = %d \n", i, len, cnt); 62 if(DFS(1, 1, 0)) { 63 printf("%d\n", i); 64 break; 65 } 66 } 67 } 68 } 69 return 0; 70 }
1 #include <cstdio> 2 #include <algorithm> 3 using std::sort; 4 const int N = 100; 5 6 int n, a[N], tot, len, cnt; 7 bool vis[N]; 8 9 inline bool cmp(const int &a, const int &b) { 10 return a > b; 11 } 12 13 bool DFS(int k, int now, int l) { 14 //printf("DFS: %d %d %d \n", k, now, l); 15 if(now == cnt + 1) { 16 return 1; 17 } 18 for(int i = k; i <= n; i++) { 19 if(vis[i]) continue; 20 //printf("%d \n", i); 21 if(a[i] + l < len) { 22 vis[i] = 1; 23 bool t = DFS(1, now, l + a[i]); 24 vis[i] = 0; 25 if(t) return 1; 26 } 27 else if(a[i] + l == len) { 28 vis[i] = 1; 29 bool t = DFS(1, now + 1, 0); 30 vis[i] = 0; 31 if(t) return 1; 32 } 33 } 34 return 0; 35 } 36 37 int main() { 38 while(scanf("%d", &n) && n) { 39 tot = 0; 40 for(int i = 1; i <= n; i++) { 41 scanf("%d", &a[i]); 42 tot += a[i]; 43 } 44 //sort(a + 1, a + n + 1, cmp); 45 /*for(int i = 1; i <= n; i++) { 46 printf("%d ", a[i]); 47 } 48 puts("");*/ 49 for(int i = a[1]; i <= tot; i++) { 50 if(tot % i == 0) { 51 len = i; 52 cnt = tot / i; 53 //printf("i = %d len = %d cnt = %d \n", i, len, cnt); 54 if(DFS(1, 1, 0)) { 55 printf("%d\n", i); 56 break; 57 } 58 } 59 } 60 } 61 return 0; 62 }
