最短路 dijkstra 優先隊列最佳化

 

Dijkstra O(E * log E)

 

/* Dijkstra O(E * log E)<br />INIT: 調用init(nv, ne)讀入邊並初始化;<br />CALL: dijkstra(n, src); dist[i]為src到i的最短距離 */<br />int cost[E], dist[V];<br />int e, pnt[E], nxt[E], head[V], prev[V], vis[V];<br />struct qnode {<br /> int v;<br /> int c;<br /> qnode(int vv = 0, int cc = 0) : v(vv), c(cc) {}<br /> bool operator<(const qnode & r) const {return c > r.c;}<br />};<br />void dijkstra(int n, const int src) {<br /> qnode mv;<br /> int i, j, k, pre;<br /> priority_queue<qnode> que;<br /> vis[src] = 1;<br /> dist[src] = 0;<br /> que.push(qnode(src, 0));<br /> for (pre = src, i = 1; i < n; i++) {<br /> for (j = head[pre]; j != -1; j = nxt[j]) {<br /> k = pnt[j];<br /> if (vis[k] == 0 && dist[pre] + cost[j] < dist[k]) {<br /> dist[k] = dist[pre] + cost[j];<br /> que.push(qnode(pnt[j], dist[k]));<br /> prev[k] = pre;<br /> }<br /> }<br /> while (!que.empty() && vis[que.top().v] == 1)<br /> que.pop();<br /> if (que.empty()) break;<br /> mv = que.top();<br /> que.pop();<br /> vis[pre = mv.v] = 1;<br /> }<br />}<br />inline void addedge(int u, int v, int c) {<br /> pnt[e] = v;<br /> cost[e] = c;<br /> nxt[e] = head[u];<br /> head[u] = e++;<br />}<br />void init(int nv, int ne) {<br /> int i, u, v;<br /> int c;<br /> e = 0;<br /> memset(head, -1, sizeof (head));<br /> memset(vis, 0, sizeof (vis));<br /> memset(prev, -1, sizeof (prev));<br /> for (i = 0; i < nv; i++) dist[i] = inf;<br /> for (i = 0; i < ne; ++i) {<br /> scanf("%d%d%d", &u, &v, &c); // %d: type of cost<br /> addedge(u, v, c); // vertex: 0 ~ n-1, 單向邊，雙向邊時加兩次即可<br /> }<br />}