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| #include <iostream>
#include <cstdio>
#include <queue>
#include <cstring>
#define maxn 5010
#define maxm 200010
#define cQ const Queue
using namespace std;
int n, m;
struct Edge {
int to, next, w;
} e[maxm * 2]; int c1, head[maxn];
inline void add_edge(int u, int v, int w) {
e[c1].to = v; e[c1].w = w;
e[c1].next = head[u]; head[u] = c1++;
}
struct Queue {
int k, v;
Queue() {}
Queue(int _k, int _v) { k = _k; v = _v; }
friend bool operator < (cQ &u, cQ &v) { return u.v > v.v; }
}; int dis[maxn], s, mst; bool vis[maxn];
priority_queue<Queue> Q;
void Prim() {
memset(dis, 127, sizeof dis); dis[s] = 0; Q.push(Queue(s, 0));
while (!Q.empty()) {
int u = Q.top().k, _w = Q.top().v; Q.pop();
if (vis[u]) continue; vis[u] = 1; mst += _w;
for (int i = head[u]; ~i; i = e[i].next) {
int v = e[i].to, w = e[i].w;
if (dis[v] > w) {
dis[v] = w;
Q.push(Queue(v, dis[v]));
}
}
}
}
int main() { memset(head, -1, sizeof head);
cin >> n >> m;
for (int i = 1; i <= m; ++i) {
int x, y, z; scanf("%d%d%d", &x, &y, &z);
add_edge(x, y, z); add_edge(y, x, z);
} s = 1; Prim();
cout << mst << endl;
return 0;
}
|