UVA11374 Airport Express

Posted 2020-10-22 嘒彼小星

题目大意：

在Iokh市中，机场快线是市民从市内去机场的首选交通工具。机场快线分为经济线和商业线两种，线路，速度和价钱都不同。你有一张商业线车票，可以做一站商业线，而其他时候只能乘坐经济线。假设换乘时间忽略不计，你的任务是找一条去机场最快的路线（翻译来源：https://www.cnblogs.com/arbitrary/archive/2013/02/06/2908099.html）

 

题解：

预处理最短路，枚举商业线即可

PE了很久。。。郁闷。。

  1 #include <iostream>
  2 #include <cstdio>
  3 #include <cstring>
  4 #include <cstdlib>
  5 #include <algorithm>
  6 #include <queue>
  7 #include <vector>
  8 #include <map>
  9 #include <string> 
 10 #include <cmath> 
 11 #define min(a, b) ((a) < (b) ? (a) : (b))
 12 #define max(a, b) ((a) > (b) ? (a) : (b))
 13 #define abs(a) ((a) < 0 ? (-1 * (a)) : (a))
 14 template<class T>
 15 inline void swap(T &a, T &b)
 16 {
 17     T tmp = a;a = b;b = tmp;
 18 }
 19 inline void read(int &x)
 20 {
 21     x = 0;char ch = getchar(), c = ch;
 22     while(ch < \'0\' || ch > \'9\') c = ch, ch = getchar();
 23     while(ch <= \'9\' && ch >= \'0\') x = x * 10 + ch - \'0\', ch = getchar();
 24     if(c == \'-\') x = -x;
 25 }
 26 const int INF = 0x3f3f3f3f;
 27 const int MAXN = 500 + 10;
 28 const int MAXM = 1000 + 10;
 29 struct Edge
 30 {
 31     int u,v,w,nxt;
 32     Edge(int _u, int _v, int _w, int _nxt){u = _u;v = _v;w = _w;nxt = _nxt;}
 33     Edge(){}
 34 }edge[MAXM << 1];
 35 int head[MAXN], cnt, dis1[MAXN], dis2[MAXN], vis[MAXN];
 36 inline void insert(int a, int b, int c){edge[++ cnt] = Edge(a,b,c,head[a]), head[a] = cnt;}
 37 struct Node
 38 {
 39     int u,w;
 40     Node(int _u, int _w){u = _u, w = _w;}
 41     Node(){}
 42 };
 43 struct cmp
 44 {
 45     bool operator()(Node a, Node b)
 46     {
 47         return a.w > b.w;
 48     }    
 49 };
 50 std::priority_queue<Node, std::vector<Node>, cmp> q;
 51 void dij(int S, int *d, int size)
 52 {    
 53     while(q.size()) q.pop();
 54     memset(d, 0x3f, size), memset(vis, 0, sizeof(vis)), d[S] = 0, q.push(Node(S, 0));
 55     while(q.size())
 56     {
 57         Node now = q.top();q.pop();
 58         if(vis[now.u]) continue;
 59         vis[now.u] = 1;
 60         for(int pos = head[now.u];pos;pos = edge[pos].nxt)
 61         {
 62             int v = edge[pos].v;
 63             if(vis[v]) continue;
 64             if(d[v] > d[now.u] + edge[pos].w) d[v] = d[now.u] + edge[pos].w, q.push(Node(v, d[v]));
 65         }
 66     }
 67 }
 68 int n,s,t,m,ans1,u,v,w,k,tmp1,tmp2,tmp3,ans,from,to,flag,stack[MAXN],top;
 69 void dfs(int u, int t, int *d)
 70 {
 71     if(u == t)
 72     {
 73         stack[++ top] = u, flag = 1;return;
 74     }
 75     for(int pos = head[u];pos;pos = edge[pos].nxt)
 76     {
 77         int v = edge[pos].v;
 78         if(d[v] == d[u] + edge[pos].w) dfs(v, t, d);
 79         if(flag)
 80         {
 81             stack[++ top] = u;
 82             return;
 83         }
 84     }
 85 }
 86 int main()
 87 {
 88     int ttt = 0;
 89     while(scanf("%d %d %d %d", &n, &s, &t, &m) != EOF)
 90     {
 91         if(ttt) putchar(\'\\n\');ttt = 1;
 92         memset(head, 0, sizeof(head)), cnt = 0, ans = INF, from = to = 0;
 93         for(int i = 1;i <= m;++ i) read(tmp1), read(tmp2), read(tmp3), insert(tmp1, tmp2, tmp3), insert(tmp2, tmp1, tmp3);
 94         dij(s, dis1, sizeof(dis1)), dij(t, dis2, sizeof(dis2)), read(k);
 95         ans = dis1[t];
 96         for(int i = 1;i <= k;++ i) 
 97         {
 98             read(u), read(v), read(w);
 99             if(ans > dis1[u] + w + dis2[v]) ans = dis1[u] + w + dis2[v], from = u, to = v;
100             if(ans > dis1[v] + w + dis2[u]) ans = dis1[v] + w + dis2[u], from = v, to = u;
101         }
102         if(ans == dis1[t])
103         {
104             flag = top = 0, dfs(s, t, dis1);
105             int tt = 0;
106             for(int i = top;i >= 1;-- i) 
107                 if(!tt) printf("%d", stack[i]), tt = 1;
108                 else printf(" %d", stack[i]);
109             printf("\\nTicket Not Used\\n");
110             printf("%d\\n", dis1[t]);
111             continue;
112         }
113         flag = top = 0, dfs(s, from, dis1);
114         int tt = 0;
115         for(int i = top;i >= 1;-- i)
116             if(!tt) printf("%d", stack[i]), tt = 1;
117             else printf(" %d", stack[i]);
118         flag = top = 0, dfs(t, to, dis2);
119         for(int i = 1;i <= top;++ i) 
120             if(!tt) printf("%d", stack[i]), tt = 1;
121             else printf(" %d", stack[i]);
122         printf("\\n%d\\n%d\\n", from, ans);
123     }
124     return 0;
125 }

UVA11374