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feat: add solutions to lc/lcof2 problems #2598

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Apr 16, 2024
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feat: add solutions to lc/lcof2 problems #2598

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cbe1a37
feat: add solutions to lc/lcof2 problems
yanglbme Apr 16, 2024
78e9e70
chore: update
yanglbme Apr 16, 2024
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204 changes: 140 additions & 64 deletions lcof2/剑指 Offer II 043. 往完全二叉树添加节点/README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -49,7 +49,15 @@

## 解法

### 方法一
### 方法一：BFS

我们可以使用一个数组 $tree$ 来存储完全二叉树的所有节点。在初始化时，我们使用一个队列 $q$ 来层序遍历给定的树，并将所有节点存储到数组 $tree$ 中。

在插入节点时，我们可以通过数组 $tree$ 来找到新节点的父节点 $p$。然后我们创建一个新节点 $node$，将其插入到数组 $tree$ 中，并将 $node$ 作为 $p$ 的左子节点或右子节点。最后返回 $p$ 的值。

在获取根节点时，我们直接返回数组 $tree$ 的第一个元素。

时间复杂度方面，初始化时需要 $O(n)$ 的时间，插入节点和获取根节点的时间复杂度均为 $O(1)$。空间复杂度为 $O(n)$。其中 $n$ 为树中节点的数量。

<!-- tabs:start -->

Expand All @@ -61,7 +69,8 @@
# self.left = left
# self.right = right
class CBTInserter:
def __init__(self, root: TreeNode):

def __init__(self, root: Optional[TreeNode]):
self.tree = []
q = deque([root])
while q:
Expand All @@ -73,24 +82,23 @@ class CBTInserter:
if node.right:
q.append(node.right)

def insert(self, v: int) -> int:
pid = (len(self.tree) - 1) >> 1
node = TreeNode(v)
def insert(self, val: int) -> int:
p = self.tree[(len(self.tree) - 1) // 2]
node = TreeNode(val)
self.tree.append(node)
p = self.tree[pid]
if p.left is None:
p.left = node
else:
p.right = node
return p.val

def get_root(self) -> TreeNode:
def get_root(self) -> Optional[TreeNode]:
return self.tree[0]


# Your CBTInserter object will be instantiated and called as such:
# obj = CBTInserter(root)
# param_1 = obj.insert(v)
# param_1 = obj.insert(val)
# param_2 = obj.get_root()
```

Expand All @@ -111,29 +119,29 @@ class CBTInserter:
* }
*/
class CBTInserter {
private List<TreeNode> tree;
private List<TreeNode> tree = new ArrayList<>();

public CBTInserter(TreeNode root) {
tree = new ArrayList<>();
Deque<TreeNode> q = new ArrayDeque<>();
q.offer(root);
while (!q.isEmpty()) {
TreeNode node = q.pollFirst();
tree.add(node);
if (node.left != null) {
q.offer(node.left);
}
if (node.right != null) {
q.offer(node.right);
for (int i = q.size(); i > 0; --i) {
TreeNode node = q.poll();
tree.add(node);
if (node.left != null) {
q.offer(node.left);
}
if (node.right != null) {
q.offer(node.right);
}
}
}
}

public int insert(int v) {
int pid = (tree.size() - 1) >> 1;
TreeNode node = new TreeNode(v);
public int insert(int val) {
TreeNode p = tree.get((tree.size() - 1) / 2);
TreeNode node = new TreeNode(val);
tree.add(node);
TreeNode p = tree.get(pid);
if (p.left == null) {
p.left = node;
} else {
Expand All @@ -150,7 +158,7 @@ class CBTInserter {
/**
* Your CBTInserter object will be instantiated and called as such:
* CBTInserter obj = new CBTInserter(root);
* int param_1 = obj.insert(v);
* int param_1 = obj.insert(val);
* TreeNode param_2 = obj.get_root();
*/
```
Expand All @@ -169,40 +177,47 @@ class CBTInserter {
*/
class CBTInserter {
public:
vector<TreeNode*> tree;

CBTInserter(TreeNode* root) {
queue<TreeNode*> q{{root}};
while (!q.empty()) {
auto node = q.front();
q.pop();
tree.push_back(node);
if (node->left) q.push(node->left);
if (node->right) q.push(node->right);
while (q.size()) {
for (int i = q.size(); i; --i) {
auto node = q.front();
q.pop();
tree.push_back(node);
if (node->left) {
q.push(node->left);
}
if (node->right) {
q.push(node->right);
}
}
}
}

int insert(int v) {
int pid = tree.size() - 1 >> 1;
TreeNode* node = new TreeNode(v);
int insert(int val) {
auto p = tree[(tree.size() - 1) / 2];
auto node = new TreeNode(val);
tree.push_back(node);
TreeNode* p = tree[pid];
if (!p->left)
if (!p->left) {
p->left = node;
else
} else {
p->right = node;
}
return p->val;
}

TreeNode* get_root() {
return tree[0];
}

private:
vector<TreeNode*> tree;
};

/**
* Your CBTInserter object will be instantiated and called as such:
* CBTInserter* obj = new CBTInserter(root);
* int param_1 = obj->insert(v);
* int param_1 = obj->insert(val);
* TreeNode* param_2 = obj->get_root();
*/
```
Expand All @@ -224,24 +239,25 @@ func Constructor(root *TreeNode) CBTInserter {
q := []*TreeNode{root}
tree := []*TreeNode{}
for len(q) > 0 {
node := q[0]
tree = append(tree, node)
q = q[1:]
if node.Left != nil {
q = append(q, node.Left)
}
if node.Right != nil {
q = append(q, node.Right)
for i := len(q); i > 0; i-- {
node := q[0]
q = q[1:]
tree = append(tree, node)
if node.Left != nil {
q = append(q, node.Left)
}
if node.Right != nil {
q = append(q, node.Right)
}
}
}
return CBTInserter{tree}
}

func (this *CBTInserter) Insert(v int) int {
pid := (len(this.tree) - 1) >> 1
node := &TreeNode{Val: v}
func (this *CBTInserter) Insert(val int) int {
p := this.tree[(len(this.tree)-1)/2]
node := &TreeNode{val, nil, nil}
this.tree = append(this.tree, node)
p := this.tree[pid]
if p.Left == nil {
p.Left = node
} else {
Expand All @@ -257,11 +273,70 @@ func (this *CBTInserter) Get_root() *TreeNode {
/**
* Your CBTInserter object will be instantiated and called as such:
* obj := Constructor(root);
* param_1 := obj.Insert(v);
* param_1 := obj.Insert(val);
* param_2 := obj.Get_root();
*/
```

```ts
/**
* Definition for a binary tree node.
* class TreeNode {
* val: number
* left: TreeNode | null
* right: TreeNode | null
* constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
* this.val = (val===undefined ? 0 : val)
* this.left = (left===undefined ? null : left)
* this.right = (right===undefined ? null : right)
* }
* }
*/

class CBTInserter {
private tree: TreeNode[] = [];

constructor(root: TreeNode | null) {
if (root === null) {
return;
}
const q: TreeNode[] = [root];
while (q.length) {
const t: TreeNode[] = [];
for (const node of q) {
this.tree.push(node);
node.left !== null && t.push(node.left);
node.right !== null && t.push(node.right);
}
q.splice(0, q.length, ...t);
}
}

insert(val: number): number {
const p = this.tree[(this.tree.length - 1) >> 1];
const node = new TreeNode(val);
this.tree.push(node);
if (p.left === null) {
p.left = node;
} else {
p.right = node;
}
return p.val;
}

get_root(): TreeNode | null {
return this.tree[0];
}
}

/**
* Your CBTInserter object will be instantiated and called as such:
* var obj = new CBTInserter(root)
* var param_1 = obj.insert(val)
* var param_2 = obj.get_root()
*/
```

```js
/**
* Definition for a binary tree node.
Expand All @@ -276,29 +351,30 @@ func (this *CBTInserter) Get_root() *TreeNode {
*/
var CBTInserter = function (root) {
this.tree = [];
if (root === null) {
return;
}
const q = [root];
while (q.length) {
const node = q.shift();
this.tree.push(node);
if (node.left) {
q.push(node.left);
}
if (node.right) {
q.push(node.right);
const t = [];
for (const node of q) {
this.tree.push(node);
node.left !== null && t.push(node.left);
node.right !== null && t.push(node.right);
}
q.splice(0, q.length, ...t);
}
};

/**
* @param {number} v
* @param {number} val
* @return {number}
*/
CBTInserter.prototype.insert = function (v) {
const pid = (this.tree.length - 1) >> 1;
const node = new TreeNode(v);
CBTInserter.prototype.insert = function (val) {
const p = this.tree[(this.tree.length - 1) >> 1];
const node = new TreeNode(val);
this.tree.push(node);
const p = this.tree[pid];
if (!p.left) {
if (p.left === null) {
p.left = node;
} else {
p.right = node;
Expand All @@ -316,7 +392,7 @@ CBTInserter.prototype.get_root = function () {
/**
* Your CBTInserter object will be instantiated and called as such:
* var obj = new CBTInserter(root)
* var param_1 = obj.insert(v)
* var param_1 = obj.insert(val)
* var param_2 = obj.get_root()
*/
```
Expand Down
37 changes: 22 additions & 15 deletions lcof2/剑指 Offer II 043. 往完全二叉树添加节点/Solution.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -11,39 +11,46 @@
*/
class CBTInserter {
public:
vector<TreeNode*> tree;

CBTInserter(TreeNode* root) {
queue<TreeNode*> q{{root}};
while (!q.empty()) {
auto node = q.front();
q.pop();
tree.push_back(node);
if (node->left) q.push(node->left);
if (node->right) q.push(node->right);
while (q.size()) {
for (int i = q.size(); i; --i) {
auto node = q.front();
q.pop();
tree.push_back(node);
if (node->left) {
q.push(node->left);
}
if (node->right) {
q.push(node->right);
}
}
}
}

int insert(int v) {
int pid = tree.size() - 1 >> 1;
TreeNode* node = new TreeNode(v);
int insert(int val) {
auto p = tree[(tree.size() - 1) / 2];
auto node = new TreeNode(val);
tree.push_back(node);
TreeNode* p = tree[pid];
if (!p->left)
if (!p->left) {
p->left = node;
else
} else {
p->right = node;
}
return p->val;
}

TreeNode* get_root() {
return tree[0];
}

private:
vector<TreeNode*> tree;
};

/**
* Your CBTInserter object will be instantiated and called as such:
* CBTInserter* obj = new CBTInserter(root);
* int param_1 = obj->insert(v);
* int param_1 = obj->insert(val);
* TreeNode* param_2 = obj->get_root();
*/
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