Dijkstra 优先队列优化

/*
建图用的邻接表，复杂度O(E*logE)
*/

struct pnode {
int num;
int len;

pnode() {}
pnode(int a, int b) : num(a), len(b) {}
bool operator < (const pnode tmp) const {
return len > tmp.len;
}
};

int dis
;
bool vis
;
int n;

void bfs(int s) {
priority_queue<pnode> q;
q.push(pnode(s, 0));
pnode u;
int v, i, res = inf;
for(i = 0; i <= n; ++i) dis[i] = inf, vis[i] = false;
dis[s] = 0;

while(!q.empty()) {
u = q.top(); q.pop();
if(u.len != dis[u.num]) continue;
if(vis[u.num])  continue;
vis[u.num] = true;

for(i = head[u.num]; i != -1; i = g[i].next) {
v = g[i].to;
if(dis[v] > u.len + g[i].val) {
dis[v] = u.len + g[i].val;
q.push(pnode(v, dis[v]));
}
}
}
}