📅  最后修改于: 2023-12-03 15:10:46.616000             🧑  作者: Mango
在两个节点之间的垂直距离称为垂直级别。如果一棵二叉树的垂直级别已经按从小到大的顺序排序,则我们称其为垂直排序二叉树。
本文将介绍如何查找给定二叉树的垂直级别是否已排序。
为了查找二叉树的垂直级别是否已排序,我们需要进行以下步骤:
我们可以使用哈希表来记录节点的垂直级别,使用快速排序等算法来对节点进行排序,最后遍历排好序的节点列表来检查垂直级别是否已排序。
class TreeNode:
def __init__(self, val):
self.val = val
self.left = None
self.right = None
def vertical_traversal(root):
if not root:
return []
# 哈希表记录节点的垂直级别和节点值
level_map = {}
min_level = max_level = 0
def dfs(node, level, col):
nonlocal level_map, min_level, max_level
if not node:
return
dfs(node.left, level + 1, col - 1)
dfs(node.right, level + 1, col + 1)
if col not in level_map:
level_map[col] = []
level_map[col].append((level, node.val))
min_level = min(min_level, col)
max_level = max(max_level, col)
dfs(root, 0, 0)
# 对节点按照垂直级别和节点值进行排序
for col in level_map:
level_map[col].sort()
# 检查排好序的节点垂直级别是否已经按照从小到大的顺序排列
prev_level = float('-inf')
for col in range(min_level, max_level + 1):
if col in level_map:
for level, val in level_map[col]:
if level < prev_level:
return False
prev_level = level
return True
class TreeNode {
int val;
TreeNode left;
TreeNode right;
TreeNode(int x) { val = x; }
}
class Solution {
public boolean isVerticalSorted(TreeNode root) {
if (root == null) return true;
HashMap<Integer, List<int[]>> levelMap = new HashMap<>(); // 哈希表记录节点的垂直级别和节点值
int minLevel = 0, maxLevel = 0;
dfs(root, 0, 0, levelMap, minLevel, maxLevel);
// 对节点按照垂直级别和节点值进行排序
for (List<int[]> vals : levelMap.values()) {
Collections.sort(vals, (a, b) -> a[0] - b[0] == 0 ? a[1] - b[1] : a[0] - b[0]);
}
// 检查排好序的节点垂直级别是否已经按照从小到大的顺序排列
int prevLevel = Integer.MIN_VALUE;
for (int col = minLevel; col <= maxLevel; col++) {
List<int[]> vals = levelMap.get(col);
if (vals != null) {
for (int[] val : vals) {
if (val[0] < prevLevel) {
return false;
}
prevLevel = val[0];
}
}
}
return true;
}
private void dfs(TreeNode node, int level, int col, HashMap<Integer, List<int[]>> levelMap, int minLevel, int maxLevel) {
if (node == null) {
return;
}
List<int[]> vals = levelMap.get(col);
if (vals == null) {
vals = new ArrayList<>();
levelMap.put(col, vals);
}
vals.add(new int[]{level, node.val});
minLevel = Math.min(minLevel, col);
maxLevel = Math.max(maxLevel, col);
dfs(node.left, level + 1, col - 1, levelMap, minLevel, maxLevel);
dfs(node.right, level + 1, col + 1, levelMap, minLevel, maxLevel);
}
}
本文介绍了如何查找二叉树的垂直级别是否已排序,需要进行垂直遍历、排序和检查三个步骤。本文提供了Python和Java的代码实现,读者可以自行进行参考。