Approach
Depth-first search
For ABC417 E — A Path in A Dictionary, the implementation follows one branch at a time, making it suitable for components, trees, backtracking, or dependency exploration.
- Define the state carried into one recursive or stack frame.
- Mark or choose the current state before exploring children.
- Combine child results or undo the choice when the branch finishes.
Code notes
- 65 lines of Python from the credited upstream file abc417_e.py.
- The implementation visibly relies on sequence storage, ordered lookup.
- No explicit loop blocks detected, together with recursive traversal.
Complexity
Count unique states for graph traversal; for backtracking, count the branching factor and maximum depth.
Check the problem constraints before deciding whether this complexity will pass.
Use this to learn the idea, then write your own version.
12 3 4def solve():5 n, m, x, y = map(int, input().split())6 x -= 17 y -= 18 9 graph = [[] for _ in range(n)]10 11 for _ in range(m):12 ai, bi = map(int, input().split())13 ai -= 114 bi -= 115 16 graph[ai].append(bi)17 graph[bi].append(ai)18 19 for g in graph:20 g.sort()21 22 visited = [False] * n23 ans = []24 25 def dfs(cur, parent=-1):26 ans.append(cur + 1)27 28 if cur == y:29 return True30 31 visited[cur] = True32 33 for to in graph[cur]:34 if to == parent:35 continue36 if visited[to]:37 continue38 39 if dfs(to, cur):40 return True41 42 ans.pop()43 44 return False45 46 dfs(x)47 print(*ans)48 49 50def main():51 import sys52 53 sys.setrecursionlimit(10**6)54 55 input = sys.stdin.readline56 57 t = int(input())58 59 for _ in range(t):60 solve()61 62 63if __name__ == "__main__":64 main()65