Snakeless path

class Graph:
    def __init__(self, nodes):
        self.nodes = nodes
        self.graph = {node: [] for node in nodes}

    def add_edge(self, a, b):
        self.graph[a].append(b)
        self.graph[b].append(a)
    def remove_edge(self, a, b):
        self.graph[a].remove(b)
        self.graph[b].remove(a)
    def bfs_path(self, start, end):
        queue = [start]
        visited = {start}
        parent = {start: None}
        idx = 0
        while idx < len(queue):
            node = queue[idx]
            idx += 1
            if node == end:
                path = []
                while node is not None:
                    path.append(node)
                    node = parent[node]
                return path[::-1]
            for neighbor in self.graph[node]:
                if neighbor not in visited:
                    visited.add(neighbor)
                    parent[neighbor] = node
                    queue.append(neighbor)
        return None
n, m = map(int, input().split())
nodes = list(range(1, n + 1))
g = Graph(nodes)
for i in range(1, n + 1):
    for j in range(i + 1, n + 1):
        g.add_edge(i, j)
for i in range(m):
    a, b = map(int, input().split())
    g.remove_edge(a, b)
path = g.bfs_path(1, n)
if path is None:
    print(0)
else:
    print(len(path))
    print(' '.join(map(str, path)))

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED

Test 18

Verdict: ACCEPTED

Test 19

Verdict: ACCEPTED

Test 20

Verdict: ACCEPTED

Test 21

Verdict: ACCEPTED

Test 22

Verdict: ACCEPTED

Test 23

Verdict: ACCEPTED

Test 24

Verdict: ACCEPTED

Test 25

Verdict: ACCEPTED

Test 26

Verdict: ACCEPTED

Test 27

Verdict: ACCEPTED

Test 28

Verdict: ACCEPTED

Test 29

Verdict: ACCEPTED

Test 30

Verdict: ACCEPTED

Test 31

Verdict: ACCEPTED

Test 32

Verdict: ACCEPTED

Test 33

Verdict: ACCEPTED

Test 34

Verdict: ACCEPTED

Test 35

Verdict: ACCEPTED

Test 36

Verdict: ACCEPTED

Test 37

Verdict: ACCEPTED

Test 38

Verdict: ACCEPTED

Test 39

Verdict: ACCEPTED

Test 40

Verdict: ACCEPTED

Test 41

Verdict: ACCEPTED

Test 42

Verdict: ACCEPTED

Test 43

Verdict: ACCEPTED

Test 44

Verdict: ACCEPTED

Test 45

Verdict: ACCEPTED

Test 46

Verdict: ACCEPTED

Test 47

Verdict: ACCEPTED

Test 48

Verdict: ACCEPTED

Test 49

Verdict: ACCEPTED

Test 50

Verdict: ACCEPTED

Test 51

Verdict: ACCEPTED

Test 52

Verdict: ACCEPTED

Test 53

Verdict: ACCEPTED

Test 54

Verdict: ACCEPTED

Test 55

Verdict: ACCEPTED

Test 56

Verdict: ACCEPTED

Test 57

Verdict: ACCEPTED

Test 58

Verdict: ACCEPTED

Test 59

Verdict: ACCEPTED

Test 60

Verdict: ACCEPTED

Test 61

Verdict: ACCEPTED

Test 62

Verdict: ACCEPTED

Test 63

Verdict: ACCEPTED

Test 64

Verdict: ACCEPTED

Test 65

Verdict: ACCEPTED

Test 66

Verdict: ACCEPTED

Test 67

Verdict: ACCEPTED

Test 68

Verdict: ACCEPTED

Test 69

Verdict: ACCEPTED

Test 70

Verdict: RUNTIME ERROR

Test 71

Verdict: RUNTIME ERROR

Test 72

Verdict: RUNTIME ERROR

Test 73

Verdict: RUNTIME ERROR

Test 74

Verdict: RUNTIME ERROR

Test 75

Verdict: RUNTIME ERROR

Test 76

Verdict: RUNTIME ERROR

Test 77

Verdict: RUNTIME ERROR

Test 78

Verdict: RUNTIME ERROR

Test 79

Verdict: RUNTIME ERROR

Test 80

Verdict: RUNTIME ERROR

Test 81

Verdict: RUNTIME ERROR

Test 82

Verdict: RUNTIME ERROR

Test 83

Verdict: RUNTIME ERROR

Test 84

Verdict: RUNTIME ERROR

Test 85

Verdict: RUNTIME ERROR

Test 86

Verdict: RUNTIME ERROR

Test 87

Verdict: RUNTIME ERROR

Test 88

Verdict: RUNTIME ERROR

Test 89

Verdict: RUNTIME ERROR