UVA

来源：互联网发布：光盘刻录自动播放软件编辑：程序博客网时间：2024/05/22 12:44

思路：通过前后两种状态建立一条边，利用Dijsktra就可以做了。

注意利用二进制优化。

AC代码

#include <cstdio>#include <cmath>#include <algorithm>#include <cstring>#include <utility>#include <string>#include <iostream>#include <map>#include <set>#include <vector>#include <queue>#include <stack>using namespace std;#pragma comment(linker, "/STACK:1024000000,1024000000") #define eps 1e-10#define inf 0x3f3f3f3f#define PI pair<int, int> typedef long long LL;const int maxn = (1 << 20) + 5, maxm = 100 + 5;int n, m, d[maxn], vis[maxn];char before[maxm][25], after[maxm][25];int cost[maxm]; struct Node{int bug, dist;Node(){}Node(int bug, int dis):bug(bug),dist(dis){}bool operator < (const Node& p) const {return dist > p.dist;}};int Dijsk(int u) {memset(d, inf, sizeof(d));memset(vis, 0, sizeof(vis));priority_queue<Node>Q;Q.push(Node(u, 0));d[u] = 0;while(!Q.empty()) {Node p = Q.top(); Q.pop();int u = p.bug;if(u == 0) return d[u];if(vis[u]) continue;vis[u] = 1;for(int i = 0; i < m; ++i) {bool ok = true;for(int j = 0; j < n; ++j) {if(before[i][j] == '+' && !(u & (1 << j))) {ok = false; break;}if(before[i][j] == '-' && (u & (1 << j))) {ok = false; break;}}if(!ok) continue; //不能打补丁 Node v = Node(u, p.dist + cost[i]);for(int j = 0; j < n; ++j) {if(after[i][j] == '-') v.bug &= ~(1 << j);if(after[i][j] == '+') v.bug |= (1 << j);}if(v.dist < d[v.bug] || d[v.bug] < 0) {d[v.bug] = v.dist;Q.push(v);}}}return -1;}int main() {int kase = 0;while(scanf("%d%d", &n, &m) == 2 && n && m) {for(int i = 0; i < m; ++i) {scanf("%d%s%s", &cost[i], before[i], after[i]);}int ans = Dijsk((1 << n) - 1);printf("Product %d\n", ++kase);if(ans == -1) printf("Bugs cannot be fixed.\n");else printf("Fastest sequence takes %d seconds.\n", ans);printf("\n");}return 0;}

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