完蛋完蛋，dijkstra都不会写了 啊啊啊啊啊

#include<bits/stdc++.h>
#define int long long
using namespace std;
constexpr int N = 5e5 + 7;
struct node{
	int v, w;
	friend bool operator < (node a, node b) {
		return a.w > b.w; 
	}
};
int n, m, k, s, t, cnt, ans = 0x3f3f3f3f;
int dis[N], h[N], to[N], val[N], nxt[N];
bool vis[N];
void add(int a, int b, int c){
	to[++cnt] = b;
	val[cnt] = c;
	nxt[cnt] = h[a];
	h[a] = cnt;
}
node tmp;
priority_queue<node> q;
void dijkstra(){
	for(int i = 1; i <= n; i++) dis[i] = 0x3f3f3f3f;
	dis[s] = 0;
	tmp.v = s, tmp.w = 0;
	q.push(tmp);
	while(!q.empty()){
		int u = q.top().v;
		q.pop();
		if(vis[u]) continue;
		vis[u] = 1;
		for(int i = h[u]; i; i = nxt[i]){
			if(dis[to[i]] > (long long)dis[u] + val[i]){
				dis[to[i]] = dis[u] + val[i];
				tmp.w = dis[to[i]], tmp.v = to[i];
				q.push(tmp);
			}
		}
	}
}
signed main(){
	freopen("P4568.in", "r", stdin);
	freopen("P4568.out", "w", stdout); 
	ios::sync_with_stdio(false);
	cin.tie(0), cout.tie(0);
	cin >> n >> m >> k;
	cin >> s >> t;
	for(int i = 0, u, v, w; i < m; i++){
		cin >> u >> v >> w;
		add(u, v, w);
		add(v, u, w);
		for(int j = 1; j <= k; j++){
			add(u + j * n, v + j * n, w);
			add(v + j * n, u + j * n, w);
			add(u + j * n - n, v + j * n, 0);
			add(v + j * n - n, u + j * n, 0);
		}
	}
	dijkstra();
	for(int j = 1; j <= k; j++){
		if(dis[t + j * n] < ans){
			ans = dis[t + j * n];
		}
	}
	cout << ans << '\n';
	return 0;
}
/*
5 6 1
0 4
0 1 5
1 2 5
2 3 5
3 4 5
2 3 3
0 2 100
*/

这是AC代码 这个代码没给过 但是重写的这个却过了！！！

#include<bits/stdc++.h>
#define int long long
using namespace std;
const int N = 1e6 + 7;
struct Edge {
    int to, next, weight;
} a[N * 20]; 
struct node{
    int dist, id;
    node() {}
    node(int dist, int id) : dist(dist), id(id) {};
    bool operator>(const node& other) const {
        return dist > other.dist;
    }
};
int n, m, k, s, t, cnt;
int head[N], vis[N], dist[N];
void addedge(int u, int v, int w) {
    a[cnt].to = v;
    a[cnt].weight = w;
    a[cnt].next = head[u];
    head[u] = cnt++;
}
void dijkstra(int s){
    memset(vis, 0, sizeof(vis));
    memset(dist, 0x3f, sizeof(dist));
    priority_queue<node, vector<node>, greater<node> > q;
    q.push(node{0, s});
    dist[s] = 0;
    while(!q.empty()){
        node t = q.top();
        q.pop();
        if(vis[t.id]) continue;
        vis[t.id] = 1;
        for(int i = head[t.id]; i != -1; i = a[i].next){
            int v = a[i].to;
            if(dist[v] > dist[t.id] + a[i].weight) {
                dist[v] = dist[t.id] + a[i].weight;
                q.push(node{dist[v], v});
            }
        }
    }
}
signed main(){
    ios::sync_with_stdio(false);
    cin.tie(0), cout.tie(0);
    memset(head, -1, sizeof head);
    cnt = 0;  
    cin >> n >> m >> k; 
    cin >> s >> t;
    for(int i = 1, x, y, w; i <= m; i++){
        cin >> x >> y >> w;
        addedge(x, y, w);
        addedge(y, x, w);
        for(int j = 1; j <= k; j++){
            addedge(x + j * n, y + j * n, w);
            addedge(y + j * n, x + j * n, w);
            addedge(x + (j - 1) * n, y + j * n, 0);
            addedge(y + (j - 1) * n, x + j * n, 0);
        }
    }
    for(int i = 1; i <= k; i++){
        addedge(t + (i - 1) * n, t + i * n, 0);
    }
    dijkstra(s);
    cout << dist[t + k * n] << '\n';
    return 0;
}