POJ2449 Remmarguts' Date

  1 #include <iostream>
  2 #include <cstdlib>
  3 #include <cstring>
  4 #include <cstdio>
  5 #include <algorithm>
  6 #include <queue>
  7 #include <vector>
  8 
  9 inline void read(int &x)
 10 {
 11     x = 0;char ch = getchar(), c = ch;
 12     while(ch < ‘0‘ || ch > ‘9‘)c = ch, ch = getchar();
 13     while(ch <= ‘9‘ && ch >= ‘0‘)x = x * 10 + ch - ‘0‘, ch = getchar();
 14     if(c == ‘-‘)x = -x;
 15 } 
 16 
 17 const int MAXN = 50000 + 10;
 18 const int MAXM = 500000 + 10;
 19 
 20 struct Edge
 21 {
 22     int u,v,w,next;
 23     Edge(int _u, int _v, int _w, int _next){u = _u;v = _v; w = _w; next = _next;}
 24     Edge(){}
 25 }edge[MAXM << 2], edge2[MAXM << 2];
 26 int head[MAXN], head2[MAXN], cnt, cnt2;
 27 
 28 inline void insert(int a, int b, int c)
 29 {
 30     edge[++cnt] = Edge(a,b,c,head[a]);
 31     head[a] = cnt;
 32 }
 33 
 34 inline void insert2(int a, int b, int c)
 35 {
 36     edge2[++cnt2] = Edge(a,b,c,head2[a]);
 37     head2[a] = cnt2;
 38 }
 39 
 40 int n,m,s,t,k;
 41 
 42 int b[MAXN], d[MAXN];
 43 
 44 struct Node
 45 {
 46     int p, d;
 47     Node(int _p, int _d){p = _p;d = _d;}
 48     Node(){}    
 49 };
 50 
 51 struct cmp
 52 {
 53     bool operator()(Node a, Node b)
 54     {
 55         return a.d > b.d;
 56     }    
 57 };
 58 
 59 std::priority_queue<Node, std::vector<Node>, cmp> q;
 60 
 61 void dijkstra()
 62 {
 63     while(q.size())q.pop(); 
 64     memset(d, 0x3f, sizeof(d));
 65     q.push(Node(t, 0));
 66     d[t] = 0;
 67     register Node tmp;
 68     while(q.size())
 69     {
 70         tmp = q.top(), q.pop();
 71         if(b[tmp.p])continue;
 72         b[tmp.p] = 1;
 73         for(register int pos = head[tmp.p];pos;pos = edge[pos].next)
 74         {
 75             int v = edge[pos].v;
 76             if(b[v])continue;
 77             if(d[v] > tmp.d + edge[pos].w)
 78                 d[v] = tmp.d + edge[pos].w, q.push(Node(v, d[v]));
 79         }
 80     }
 81 }
 82 
 83 struct cmpp
 84 {
 85     bool operator()(Node a, Node b)
 86     {
 87         return a.d + d[a.p] > b.d + d[b.p];
 88     }    
 89 };
 90 
 91 std::priority_queue <Node, std::vector<Node>, cmpp> q2;
 92 
 93 int step;//拓展次数 
 94 
 95 void abfs()
 96 {
 97      step = 0;
 98      while(q2.size())q2.pop(); 
 99      q2.push(Node(s, 0));
100      register Node tmp;
101      if(d[s] == d[0])
102      {
103          printf("-1\n");
104          return;
105      }
106      while(q2.size())
107      {
108          tmp = q2.top(),q2.pop();
109          if(tmp.p == t) ++ step;
110          if(step == k)
111          {
112              printf("%d\n", tmp.d);
113              return;
114          }
115          for(register int pos = head2[tmp.p];pos;pos = edge2[pos].next)
116          {
117              int v = edge2[pos].v;
118              q2.push(Node(edge2[pos].v, tmp.d + edge2[pos].w));
119          }
120      }
121      printf("-1\n");
122 }
123 
124 int main()
125 {
126     register int tmp1, tmp2, tmp3;
127     while(scanf("%d %d", &n, &m) != EOF && (n + m))
128     {
129         memset(b, 0, sizeof(b));
130         memset(head, 0, sizeof(head));
131         memset(head2, 0, sizeof(head2));
132         memset(edge, 0, sizeof(edge));
133         memset(edge2, 0, sizeof(edge2));
134         cnt = cnt2 = 0;
135         for(register int i = 1;i <= m;++ i)
136         {
137             read(tmp1), read(tmp2), read(tmp3);
138             insert2(tmp1, tmp2, tmp3);
139             insert(tmp2, tmp1, tmp3);
140         }
141         read(s), read(t), read(k);
142         if(t == s)++ k;
143         dijkstra();
144         abfs();
145     }
146     return 0;
147 }