AOJ ALDS1_7_C Tree Walk
備忘録
問題
http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=ALDS1_7_C&lang=ja
回答
import sys, os, math, bisect, itertools, collections, heapq, queue, copy, array # from scipy.sparse.csgraph import csgraph_from_dense, floyd_warshall # from decimal import Decimal # from collections import defaultdict, deque sys.setrecursionlimit(10000000) ii = lambda: int(sys.stdin.buffer.readline().rstrip()) il = lambda: list(map(int, sys.stdin.buffer.readline().split())) fl = lambda: list(map(float, sys.stdin.buffer.readline().split())) iln = lambda n: [int(sys.stdin.buffer.readline().rstrip()) for _ in range(n)] iss = lambda: sys.stdin.buffer.readline().decode().rstrip() sl = lambda: list(map(str, sys.stdin.buffer.readline().decode().split())) isn = lambda n: [sys.stdin.buffer.readline().decode().rstrip() for _ in range(n)] lcm = lambda x, y: (x * y) // math.gcd(x, y) MOD = 10 ** 9 + 7 MAX = float('inf') class BinaryNode: def __init__(self, node, left, right): self.node = node self.left = left self.right = right class BinaryTree: def __init__(self, N): self.tree = [-1] * N self.parent = [-1] * N def insert_node(self, N, node): self.tree[N] = node if node.left is not None: self.parent[node.left] = N if node.right is not None: self.parent[node.right] = N def get_root(self): for n in range(len(self.parent)): if self.parent[n] == -1: return n def preorder(self, N): ret = [N] if self.tree[N].left is not None: ret.extend(self.preorder(self.tree[N].left)) if self.tree[N].right is not None: ret.extend(self.preorder(self.tree[N].right)) return ret def inorder(self, N): ret = [] if self.tree[N].left is not None: ret.extend(self.inorder(self.tree[N].left)) ret.append(N) if self.tree[N].right is not None: ret.extend(self.inorder(self.tree[N].right)) return ret def postorder(self, N): ret = [] if self.tree[N].left is not None: ret.extend(self.postorder(self.tree[N].left)) if self.tree[N].right is not None: ret.extend(self.postorder(self.tree[N].right)) ret.append(N) return ret def main(): if os.getenv("LOCAL"): sys.stdin = open("input.txt", "r") N = ii() tree = BinaryTree(N) for n in range(N): n, left, right = il() if left == -1: left = None if right == -1: right = None tree.insert_node(n, BinaryNode(n, left, right)) print('Preorder') print('', *tree.preorder(tree.get_root())) print('Inorder') print('', *tree.inorder(tree.get_root())) print('Postorder') print('', *tree.postorder(tree.get_root())) if __name__ == '__main__': main()
回答
螺旋本より、二分木入門。
ノード数の制約も小さいので、自作クラスで回答を行った。
入力時、各ノードをBinaryNode
クラスとして、
BinaryTree
に追加する。
木に追加する際に、各ノードの親ノードを記録しておく。
後はルートノードから指示された通りに探索を行なうだけ。
出力はフォーマットするまでもないかな、と適当に出力。