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import java.util.*;
public class Dijkstra {
static int distance(ArrayList<Integer>[] adj, ArrayList<Integer>[] cost, int s, int t) {
if (s == t)
return 0;
int[] dist = new int[adj.length];
//int[] prev = new int[adj.length];
boolean[] visited = new boolean[adj.length];
for (int i = 0; i < dist.length; i++) {
dist[i] = Integer.MAX_VALUE;
//prev[i] = -1;
}
dist[s] = 0;
PriorityQueue<Integer> vertexQ;
vertexQ = new PriorityQueue<Integer>(Comparator.comparingInt(a -> dist[a]));
vertexQ.add(s);
while (!vertexQ.isEmpty()) {
int u = vertexQ.remove();
if (visited[u]) {
continue;
}
visited[u] = true;
if (adj[u].size() > 0) {
for (int i = 0; i < adj[u].size(); i++) {
if (dist[adj[u].get(i)] > dist[u] + cost[u].get(i)) {
dist[adj[u].get(i)] = dist[u] + cost[u].get(i);
//prev[adj[u].get(i)] = u;
vertexQ.add(adj[u].get(i));
}
}
}
}
if (dist[t] == Integer.MAX_VALUE)
return -1;
return dist[t];
}
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int n = scanner.nextInt();
int m = scanner.nextInt();
ArrayList<Integer>[] adj = (ArrayList<Integer>[]) new ArrayList[n];
ArrayList<Integer>[] cost = (ArrayList<Integer>[]) new ArrayList[n];
for (int i = 0; i < n; i++) {
adj[i] = new ArrayList<Integer>();
cost[i] = new ArrayList<Integer>();
}
for (int i = 0; i < m; i++) {
int x, y, w;
x = scanner.nextInt();
y = scanner.nextInt();
w = scanner.nextInt();
adj[x - 1].add(y - 1);
cost[x - 1].add(w);
}
int x = scanner.nextInt() - 1;
int y = scanner.nextInt() - 1;
System.out.println(distance(adj, cost, x, y));
}
}
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