UVa/11367 - Full tank?/11367.cpp

   1 /*
   2   Time limit exceeded!
   3  */
   4 #include <iostream>
   5 #include <vector>
   6 #include <queue>
   7 //#include <cassert>
   8
   9 using namespace std;
  10
  11 const int MAXN = 1000, MAXC = 100;
  12
  13 struct edge{
  14   int i, g, w;
  15   edge(){}
  16   edge(int I, int G, int W) : i(I), g(G), w(W) {}
  17   bool operator < (const edge &that) const {
  18     return w > that.w;
  19   }
  20 };
  21
  22 int p[MAXN], d[MAXN][MAXC+1], n;
  23 vector<edge> g[MAXN];
  24
  25
  26 int dijkstra(const int &start, const int &end, const int &c){
  27   for (int i=0; i<n; ++i)
  28     for (int j=0; j<=c; ++j)
  29       d[i][j] = INT_MAX;
  30
  31   priority_queue<edge> q;
  32   q.push(edge(start, 0, 0));
  33   d[start][0] = 0;
  34
  35   while (q.size()){
  36     edge u = q.top();
  37     q.pop();
  38
  39     //printf("popped <%d, %d, %d>\n", u.i, u.g, u.w);
  40     if (u.i == end){
  41       return u.w;
  42     }
  43     if (d[u.i][u.g] < u.w) continue;
  44
  45     vector<edge> &v = g[u.i];
  46     for (int j=0; j<v.size(); ++j){
  47       int distance = v[j].w;
  48       int neighbor = v[j].i;
  49       for (int k = distance - u.g; k <= c + distance - u.g; ++k){
  50         int new_gas = u.g - distance + k;
  51         if (k >= 0 && 0 <= new_gas && u.g + k <= c ){
  52           int w_extra = k*p[u.i];
  53           //assert(w_extra >= 0);
  54           if (u.w + w_extra < d[neighbor][new_gas]){
  55             d[neighbor][new_gas] = u.w + w_extra;
  56             q.push(edge(neighbor, new_gas, u.w + w_extra));
  57             //printf("  pushed <%d, %d, %d>\n", neighbor, new_gas, u.w + w_extra);
  58           }
  59         }
  60       }
  61     }
  62   }
  63   return INT_MAX;
  64
  65 }
  66
  67 int main(){
  68   int m;
  69   scanf("%d %d", &n, &m);
  70   for (int i=0; i<n; ++i){
  71     scanf("%d", &p[i]);
  72   }
  73
  74   while (m--){
  75     int u, v, d;
  76     scanf("%d %d %d", &u, &v, &d);
  77     g[u].push_back(edge(v, 0, d));
  78     g[v].push_back(edge(u, 0, d));
  79   }
  80
  81   int q;
  82   scanf("%d", &q);
  83   while (q--){
  84     int c, s, e;
  85     scanf("%d %d %d", &c, &s, &e);
  86     int t = dijkstra(s, e, c);
  87     if (t < INT_MAX){
  88       printf("%d\n", t);
  89     }else{
  90       printf("impossible\n");
  91     }
  92   }
  93   return 0;
  94 }