http://poj.org/problem?id=2449
1 #include <iostream> 2 #include <queue> 3 #include <stdio.h> 4 using namespace std; 5 6 const int INF = 1e9; 7 const int maxr = 100009; 8 const int maxn = 1009; 9 int n, m, index = 1, to1[maxr], to2[maxr], w1[maxr], w2[maxr], pre1[maxr], pre2[maxr], p1[maxn], p2[maxn], dis[maxn]; 10 bool vis[maxn]; 11 12 struct Node{ 13 int v, d; 14 bool operator < (const Node &b) const { 15 return dis[v] + d > dis[b.v] + b.d; 16 } 17 }; 18 19 int K_road(int s, int t, int k){ 20 for(int i = 1; i <= n; ++i) dis[i] = INF; 21 dis[t] = 0; 22 queue<int> q; 23 q.push(t); 24 while(!q.empty()){ 25 int v = q.front(); q.pop(); 26 vis[v] = false; 27 for(int i = p2[v]; i; i = pre2[i]) if(dis[v] + w2[i] < dis[to2[i]]){ 28 dis[to2[i]] = dis[v] + w2[i]; 29 if(!vis[to2[i]]){ 30 q.push(to2[i]); 31 vis[to2[i]] = true; 32 } 33 } 34 } 35 if(dis[s] == INF) return -1; 36 int cnt = (s == t ? -1 : 0); 37 priority_queue<Node> pq; 38 Node a, b; 39 a.v = s, a.d = 0; 40 pq.push(a); 41 while(!pq.empty()){ 42 a = pq.top(); pq.pop(); 43 int v = a.v, d = a.d; 44 if(v == t) cnt++; 45 if(cnt == k) return d; 46 for(int i = p1[v]; i; i = pre1[i]){ 47 b.v = to1[i], b.d = d + w1[i]; 48 pq.push(b); 49 } 50 } 51 return -1; 52 } 53 int main(){ 54 scanf("%d%d", &n, &m); 55 int x, y, z; 56 for(int i = 0; i < m; ++i){ 57 scanf("%d%d%d", &x, &y, &z); 58 to1[index] = y, w1[index] = z, pre1[index] = p1[x], p1[x] = index; 59 to2[index] = x, w2[index] = z, pre2[index] = p2[y], p2[y] = index++; 60 } 61 int s, t, k; 62 scanf("%d%d%d", &s, &t, &k); 63 printf("%d ", K_road(s, t, k)); 64 return 0; 65 }
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