最短路relax + 带剪枝的搜索，个人觉得此剪枝十分牛逼，如果不参照题解我是反应不过来的。
1 /* 2 ID:esxgx1 3 LANG:C++ 4 PROG:B 5 */ 6 #include <cstdio> 7 #include <iostream> 8 #include <cstring> 9 #include <algorithm> 10 using namespace std; 11 12 #define INF 0x3f3f3f3f 13 14 #define MAXN 31 15 int N; 16 int dis[MAXN][MAXN]; 17 int later_time[MAXN]; 18 19 #define pp { 20 int o = time + dis[i][j]; 21 if (sumtime + o*(N - layers) >= mint) continue; 22 if (blk & (1<<j)) { 23 if (layers + 1 >= N) { 24 if (mint > sumtime + o) 25 mint = sumtime + o; 26 } else dfs(layers + 1, blk, sumtime + o, o, j); 27 } 28 } 29 30 int mint; 31 32 void dfs(int layers, int blk, int sumtime, int time, int i) 33 { 34 blk ^= 1<<i; 35 for(int j=1; j<i; ++j) 36 if (blk & (1<<j) && time + dis[i][j] > later_time[j]) return; 37 for(int j=i+1; j<N; ++j) 38 if (blk & (1<<j) && time + dis[i][j] > later_time[j]) return; 39 for(int j=1; j<i; ++j) pp 40 for(int j=i+1; j<N; ++j) pp 41 } 42 43 int main(void) 44 { 45 #ifndef ONLINE_JUDGE 46 freopen("in.txt", "r", stdin); 47 #endif 48 while(scanf("%d", &N) > 0) { 49 //memset(blk, 0, sizeof(blk)); 50 for(int i=0; i<N; ++i) 51 for(int j=0; j<N; ++j) 52 scanf("%d", &dis[i][j]); 53 for(int i=1; i<N; ++i) 54 scanf("%d", &later_time[i]); 55 for(int k = 0; k<N; ++k) 56 for(int i=0; i<N; ++i) 57 if (dis[i][k]) 58 for(int j=0; j<N; ++j) 59 if (dis[k][j] && dis[i][j] > dis[i][k] + dis[k][j]) 60 dis[i][j] = dis[i][k] + dis[k][j]; 61 mint = INF; 62 dfs(1,~0, 0, 0, 0); 63 if (mint >= INF) printf("-1 "); 64 else printf("%d ", mint); 65 } 66 return 0; 67 }
| 2014-07-26 01:36:39 | Accepted | 4848 | 265MS | 288K | 1469 B | G++ |