Internet connection

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

import static java.util.stream.Collectors.toList;

public class InternetConnection {

    public static class Node {
        int target;
        long speed;

        public Node(int target, long speed) {
            this.target = target;
            this.speed = speed;
        }
    }

    public static class Input {
        int n;
        int m;

        Map<Integer, List<Node>> nodes;

        public Input(int n, int m, Map<Integer, List<Node>> nodes) {
            this.n = n;
            this.m = m;
            this.nodes = nodes;
        }
    }

    private static Input getInput() {
        try (BufferedReader reader = new BufferedReader( new InputStreamReader( System.in ) )) {
            var line = reader.readLine();
            var split = line.split(" ");
            int n = Integer.parseInt(split[0]);
            int m = Integer.parseInt(split[1]);
            Map<Integer, List<Node>> nodes = new HashMap<>();
            for (int i = 0; i < m; i++) {
                line = reader.readLine();
                split = line.split(" ");
                int a = Integer.parseInt(split[0]);
                int b = Integer.parseInt(split[1]);
                long c = Long.parseLong(split[2]);
                if (!nodes.containsKey(a)) {
                    nodes.put(a, new ArrayList<>());
                }
                nodes.get(a).add(new Node(b, c));
            }
            return new Input(n, m, nodes);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    public static void main(String[] args) {
        var input = getInput();

        System.out.println(new InternetConnection(input).find());
    }

    private final Input input;

    public InternetConnection(Input input) {
        this.input = input;
    }

    public long find() {
        var paths = findAllPaths();
        long sum = 0L;

        for (var path : paths) {
            var minSpeed = findMinSpeed(path);
            sum += minSpeed;
            for (var node : path) {
                node.speed -= minSpeed;
            }
        }

        return sum;
    }

    private long getSpeed(Node from, Node to) {
        for (var node : this.input.nodes.get(from.target)) {
            if (node.target == to.target) {
                return node.speed;
            }
        }
        return -1;
    }

    private long findMinSpeed(List<Node> path) {
        long min = Long.MAX_VALUE;

        for (int i = 0; i < path.size() - 1; i++) {
            var speed = getSpeed(path.get(i), path.get(i + 1));
            if (speed < min) {
                min = speed;
            }
        }

        return min;
    }

    private Set<List<Node>> findAllPaths() {
        var start = this.input.nodes.get(1);
        Set<List<Node>> results = new HashSet<>();
        start.forEach(node -> this.findPath(new ArrayList<>(List.of(node)), results));
        return results;
    }

    private void findPath(List<Node> currentPath, Set<List<Node>> results) {
        var last = currentPath.get(currentPath.size() - 1);
        if (last.target == this.input.n) {
            results.add(currentPath);
            return;
        }

        for (Node n : this.input.nodes.get(last.target)) {
            var newPath = new ArrayList<>(currentPath);
            newPath.add(n);
            findPath(newPath, results);
        }
    }
}

Test 1

Verdict: WRONG ANSWER

Test 2

Verdict: WRONG ANSWER

Test 3

Verdict: WRONG ANSWER

Test 4

Verdict: WRONG ANSWER

Test 5

Verdict: WRONG ANSWER

Test 6

Verdict: TIME LIMIT EXCEEDED

Test 7

Verdict: TIME LIMIT EXCEEDED

Test 8

Verdict: TIME LIMIT EXCEEDED

Test 9

Verdict: TIME LIMIT EXCEEDED

Test 10

Verdict: TIME LIMIT EXCEEDED

Test 11

Verdict: WRONG ANSWER

Test 12

Verdict: RUNTIME ERROR

Exception in thread "main" java.lang.NullPointerException
	at InternetConnection.findAllPa...

Test 13

Verdict: WRONG ANSWER

Test 14

Verdict: RUNTIME ERROR

Exception in thread "main" java.lang.NullPointerException
	at InternetConnection.findPath(...

Test 15

Verdict: ACCEPTED

Test 16

Verdict: RUNTIME ERROR

Exception in thread "main" java.lang.NullPointerException
	at InternetConnection.findAllPa...

Test 17

Verdict: RUNTIME ERROR

Exception in thread "main" java.lang.NullPointerException
	at InternetConnection.findAllPa...

Test 18

Verdict: ACCEPTED

Test 19

Verdict: ACCEPTED

Test 20

Verdict: WRONG ANSWER

Test 21

Verdict: TIME LIMIT EXCEEDED

Test 22

Verdict: TIME LIMIT EXCEEDED