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feat(csharp): add csharp code for array binary tree (#632)

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hpstory
2023-07-20 18:54:40 +08:00
committed by GitHub
parent 2b7d7aa827
commit 2af77ff565
3 changed files with 184 additions and 37 deletions
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79
codes/csharp/utils/TreeNode.cs
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@ -13,50 +13,59 @@ public class TreeNode {
public TreeNode? left; // 左子节点引用
public TreeNode? right; // 右子节点引用
/* 构造方法 */
public TreeNode(int x) {
val = x;
}
/* Generate a binary tree given an array */
public static TreeNode? ListToTree(List<int?> arr) {
if (arr.Count == 0 || arr[0] == null)
return null;
// 序列化编码规则请参考：
// https://www.hello-algo.com/chapter_tree/array_representation_of_tree/
// 二叉树的数组表示：
// [1, 2, 3, 4, None, 6, 7, 8, 9, None, None, 12, None, None, 15]
// 二叉树的链表表示：
// /——— 15
// /——— 7
// /——— 3
// | \——— 6
// | \——— 12
// ——— 1
// \——— 2
// | /——— 9
// \——— 4
// \——— 8
TreeNode root = new TreeNode(arr[0]!.Value);
Queue<TreeNode> queue = new Queue<TreeNode>();
queue.Enqueue(root);
int i = 0;
while (queue.Count != 0) {
TreeNode node = queue.Dequeue();
if (++i >= arr.Count) break;
if (arr[i] != null) {
node.left = new TreeNode((int)arr[i]);
queue.Enqueue(node.left);
}
if (++i >= arr.Count) break;
if (arr[i] != null) {
node.right = new TreeNode((int)arr[i]);
queue.Enqueue(node.right);
}
/* 将列表反序列化为二叉树：递归 */
private static TreeNode? ListToTreeDFS(List<int?> arr, int i) {
if (i < 0|| i >= arr.Count || !arr[i].HasValue) {
return null;
}
TreeNode root = new TreeNode(arr[i].Value);
root.left = ListToTreeDFS(arr, 2 * i + 1);
root.right = ListToTreeDFS(arr, 2 * i + 2);
return root;
}
/* Serialize a binary tree to a list */
public static List<int?> TreeToList(TreeNode root) {
List<int?> list = new();
if (root == null) return list;
Queue<TreeNode?> queue = new();
while (queue.Count != 0) {
TreeNode? node = queue.Dequeue();
if (node != null) {
list.Add(node.val);
queue.Enqueue(node.left);
queue.Enqueue(node.right);
} else {
list.Add(null);
}
/* 将列表反序列化为二叉树 */
public static TreeNode? ListToTree(List<int?> arr) {
return ListToTreeDFS(arr, 0);
}
/* 将二叉树序列化为列表：递归 */
private static void TreeToListDFS(TreeNode? root, int i, List<int?> res) {
if (root == null)
return;
while (i >= res.Count) {
res.Add(null);
}
return list;
res[i] = root.val;
TreeToListDFS(root.left, 2 * i + 1, res);
TreeToListDFS(root.right, 2 * i + 2, res);
}
/* 将二叉树序列化为列表 */
public static List<int?> treeToList(TreeNode root) {
List<int?> res = new List<int?>();
TreeToListDFS(root, 0, res);
return res;
}
}