优先队列优化的迪杰斯特拉算法

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
using namespace std;
const int NI = 100005;
const int INF = 0x3f3f3f3f;
struct node {
    int num, dis;
    node(int n, int d) {
        num = n; dis = d;
    }
    bool operator < (const node &a) const{
        if(dis == a.dis) return num < a.num;
        return dis < a.dis;
    }
};
vector g[NI];
int dis[NI];
int n, a, b, c;
void dijkstra(int s) {
    memset(dis, INF, sizeof(dis));
    dis[s] = 0;
    priority_queue q;
    q.push(node(s, dis[s]));
    while(!q.empty()) {
        node x = q.top(); q.pop();
        for(int i = 0; i < (int)g[x.num].size(); i++) {
            node y = g[x.num][i];
            if(x.dis + y.dis < dis[y.num]) {
                dis[y.num] = x.dis + y.dis;
                q.push(node(y.num, dis[y.num]));
            }
        }
    }
}
int main() {
    scanf("%d", &n);
    for(int i = 0; i < n-1; i++) {
        scanf("%d%d%d", &a, &b, &c);
        g[a].push_back(node(b, c));
        g[b].push_back(node(a, c));
    }
    dijkstra(1);
    int maxn = -1, maxx = -1;
    for(int i = 1; i <= n; i++) {
        if(dis[i] > maxn) {
            maxn = dis[i]; maxx = i;
        }
    }
    dijkstra(maxx);
    maxn = -1, maxx = -1;
    for(int i = 1; i <= n; i++) {
        if(dis[i] > maxn) {
            maxn = dis[i]; maxx = i;
        }
    }
    long long res = 0;
    for(int i = 0; i < dis[maxx]; i++) {
        res += i + 11;
    }
    printf("%I64d\n", res);
    return 0;
}