C10第8章优先队列的Dijkstra算法（堆优化）

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3 3
1 2 5
2 3 5
3 1 2

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#include <bits/stdc++.h>
using namespace std;
const int N = 1e3 + 9;
const int M = 1e4 + 9;
typedef pair<int, int> pii;

struct edge {
    int v, w, next;
} e[M << 1];

int head[N], len;
void init() {
    memset(head, -1, sizeof(head));
    len = 0;
}
void add(int u, int v, int w) {
    e[len] = {v, w, head[u]};
    head[u] = len++;
}

int n, m;
int dis[N];
bool vis[N];
void dijkstra(int u) {
    memset(vis, false, sizeof(vis));
    memset(dis, 0x3f, sizeof(dis));
    priority_queue<pii, vector<pii>, greater<>> q;
    q.push({dis[u] = 0, u});
    while (q.size()) {
        int u = q.top().second;
        q.pop();
        if (vis[u]) {
            continue;
        }
        vis[u] = true;
        for (int j = head[u]; ~j; j = e[j].next) {
            int v = e[j].v;
            int w = e[j].w;
            if (!vis[v] && dis[v] > dis[u] + w) {
                q.push({dis[v] = dis[u] + w, v});
            }
        }
    }
}
int main() {
    init();
    int u, v, w;
    cin >> n >> m;
    while (m--) {
        cin >> u >> v >> w;
        add(u, v, w);
        add(v, u, w);
    }
    dijkstra(1);
    cout << dis[n] << endl;
    return 0;
}