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feat: add solutions to lc problem: No.0199 (#3913)
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No.0199.Binary Tree Right Side View
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@yanglbme
yanglbme authored Dec 31, 2024
1 parent 836a3a6 commit da45883
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256 changes: 185 additions & 71 deletions solution/0100-0199/0199.Binary Tree Right Side View/README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -80,7 +80,7 @@ tags:

### 方法一：BFS

使用 BFS 层序遍历二叉树，每层最后一个节点即为该层的右视图节点。
我们可以使用广度优先搜索，定义一个队列 $\textit{q}$，将根节点放入队列中。每次从队列中取出当前层的所有节点，对于当前节点，我们先判断右子树是否存在，若存在则将右子树放入队列中；再判断左子树是否存在，若存在则将左子树放入队列中。这样每次取出队列中的第一个节点即为该层的右视图节点。

时间复杂度 $O(n)$，空间复杂度 $O(n)$。其中 $n$ 为二叉树节点个数。

Expand All @@ -102,13 +102,13 @@ class Solution:
return ans
q = deque([root])
while q:
ans.append(q[-1].val)
ans.append(q[0].val)
for _ in range(len(q)):
node = q.popleft()
if node.left:
q.append(node.left)
if node.right:
q.append(node.right)
if node.left:
q.append(node.left)
return ans
```

Expand Down Expand Up @@ -139,15 +139,15 @@ class Solution {
Deque<TreeNode> q = new ArrayDeque<>();
q.offer(root);
while (!q.isEmpty()) {
ans.add(q.peekLast().val);
for (int n = q.size(); n > 0; --n) {
ans.add(q.peekFirst().val);
for (int k = q.size(); k > 0; --k) {
TreeNode node = q.poll();
if (node.left != null) {
q.offer(node.left);
}
if (node.right != null) {
q.offer(node.right);
}
if (node.left != null) {
q.offer(node.left);
}
}
}
return ans;
Expand Down Expand Up @@ -177,17 +177,17 @@ public:
return ans;
}
queue<TreeNode*> q{{root}};
while (!q.empty()) {
ans.emplace_back(q.back()->val);
for (int n = q.size(); n; --n) {
TreeNode* node = q.front();
while (q.size()) {
ans.push_back(q.front()->val);
for (int k = q.size(); k; --k) {
auto node = q.front();
q.pop();
if (node->left) {
q.push(node->left);
}
if (node->right) {
q.push(node->right);
}
if (node->left) {
q.push(node->left);
}
}
}
return ans;
Expand All @@ -212,16 +212,16 @@ func rightSideView(root *TreeNode) (ans []int) {
}
q := []*TreeNode{root}
for len(q) > 0 {
ans = append(ans, q[len(q)-1].Val)
for n := len(q); n > 0; n-- {
ans = append(ans, q[0].Val)
for k := len(q); k > 0; k-- {
node := q[0]
q = q[1:]
if node.Left != nil {
q = append(q, node.Left)
}
if node.Right != nil {
q = append(q, node.Right)
}
if node.Left != nil {
q = append(q, node.Left)
}
}
}
return
Expand All @@ -246,23 +246,24 @@ func rightSideView(root *TreeNode) (ans []int) {
*/

function rightSideView(root: TreeNode | null): number[] {
const ans: number[] = [];
if (!root) {
return [];
return ans;
}
let q = [root];
const ans: number[] = [];
while (q.length) {
const nextq: TreeNode[] = [];
ans.push(q.at(-1)!.val);
const q: TreeNode[] = [root];
while (q.length > 0) {
ans.push(q[0].val);
const nq: TreeNode[] = [];
for (const { left, right } of q) {
if (left) {
nextq.push(left);
}
if (right) {
nextq.push(right);
nq.push(right);
}
if (left) {
nq.push(left);
}
}
q = nextq;
q.length = 0;
q.push(...nq);
}
return ans;
}
Expand Down Expand Up @@ -294,32 +295,71 @@ use std::collections::VecDeque;
use std::rc::Rc;
impl Solution {
pub fn right_side_view(root: Option<Rc<RefCell<TreeNode>>>) -> Vec<i32> {
let mut res = vec![];
let mut ans = vec![];
if root.is_none() {
return res;
return ans;
}
let mut q = VecDeque::new();
q.push_back(root);
while !q.is_empty() {
let n = q.len();
res.push(q[n - 1].as_ref().unwrap().borrow().val);
for _ in 0..n {
let k = q.len();
ans.push(q[0].as_ref().unwrap().borrow().val);
for _ in 0..k {
if let Some(node) = q.pop_front().unwrap() {
let mut node = node.borrow_mut();
if node.left.is_some() {
q.push_back(node.left.take());
}
if node.right.is_some() {
q.push_back(node.right.take());
}
if node.left.is_some() {
q.push_back(node.left.take());
}
}
}
}
res
ans
}
}
```

#### JavaScript

```js
/**
* Definition for a binary tree node.
* function TreeNode(val, left, right) {
* this.val = (val===undefined ? 0 : val)
* this.left = (left===undefined ? null : left)
* this.right = (right===undefined ? null : right)
* }
*/
/**
* @param {TreeNode} root
* @return {number[]}
*/
var rightSideView = function (root) {
const ans = [];
if (!root) {
return ans;
}
const q = [root];
while (q.length > 0) {
ans.push(q[0].val);
const nq = [];
for (const { left, right } of q) {
if (right) {
nq.push(right);
}
if (left) {
nq.push(left);
}
}
q.length = 0;
q.push(...nq);
}
return ans;
};
```

<!-- tabs:end -->

<!-- solution:end -->
Expand All @@ -345,13 +385,13 @@ impl Solution {
# self.right = right
class Solution:
def rightSideView(self, root: Optional[TreeNode]) -> List[int]:
def dfs(node, depth):
if node is None:
def dfs(root: Optional[TreeNode], depth: int) -> None:
if root is None:
return
if depth == len(ans):
ans.append(node.val)
dfs(node.right, depth + 1)
dfs(node.left, depth + 1)
if len(ans) == depth:
ans.append(root.val)
dfs(root.right, depth + 1)
dfs(root.left, depth + 1)

ans = []
dfs(root, 0)
Expand Down Expand Up @@ -384,15 +424,15 @@ class Solution {
return ans;
}

private void dfs(TreeNode node, int depth) {
if (node == null) {
private void dfs(TreeNode root, int depth) {
if (root == null) {
return;
}
if (depth == ans.size()) {
ans.add(node.val);
if (ans.size() == depth) {
ans.add(root.val);
}
dfs(node.right, depth + 1);
dfs(node.left, depth + 1);
dfs(root.right, depth + 1);
dfs(root.left, depth + 1);
}
}
```
Expand All @@ -415,15 +455,15 @@ class Solution {
public:
vector<int> rightSideView(TreeNode* root) {
vector<int> ans;
function<void(TreeNode*, int)> dfs = [&](TreeNode* node, int depth) {
if (!node) {
auto dfs = [&](this auto&& dfs, TreeNode* root, int depth) -> void {
if (!root) {
return;
}
if (depth == ans.size()) {
ans.emplace_back(node->val);
if (ans.size() == depth) {
ans.push_back(root->val);
}
dfs(node->right, depth + 1);
dfs(node->left, depth + 1);
dfs(root->right, depth + 1);
dfs(root->left, depth + 1);
};
dfs(root, 0);
return ans;
Expand All @@ -444,15 +484,15 @@ public:
*/
func rightSideView(root *TreeNode) (ans []int) {
var dfs func(*TreeNode, int)
dfs = func(node *TreeNode, depth int) {
if node == nil {
dfs = func(root *TreeNode, depth int) {
if root == nil {
return
}
if depth == len(ans) {
ans = append(ans, node.Val)
if len(ans) == depth {
ans = append(ans, root.Val)
}
dfs(node.Right, depth+1)
dfs(node.Left, depth+1)
dfs(root.Right, depth+1)
dfs(root.Left, depth+1)
}
dfs(root, 0)
return
Expand All @@ -478,21 +518,95 @@ func rightSideView(root *TreeNode) (ans []int) {

function rightSideView(root: TreeNode | null): number[] {
const ans = [];
const dfs = (node: TreeNode | null, depth: number) => {
if (!node) {
const dfs = (root: TreeNode | null, depth: number) => {
if (!root) {
return;
}
if (depth == ans.length) {
ans.push(node.val);
if (ans.length == depth) {
ans.push(root.val);
}
dfs(node.right, depth + 1);
dfs(node.left, depth + 1);
dfs(root.right, depth + 1);
dfs(root.left, depth + 1);
};
dfs(root, 0);
return ans;
}
```

#### Rust

```rust
// Definition for a binary tree node.
// #[derive(Debug, PartialEq, Eq)]
// pub struct TreeNode {
// pub val: i32,
// pub left: Option<Rc<RefCell<TreeNode>>>,
// pub right: Option<Rc<RefCell<TreeNode>>>,
// }
//
// impl TreeNode {
// #[inline]
// pub fn new(val: i32) -> Self {
// TreeNode {
// val,
// left: None,
// right: None
// }
// }
// }
use std::cell::RefCell;
use std::rc::Rc;
impl Solution {
pub fn right_side_view(root: Option<Rc<RefCell<TreeNode>>>) -> Vec<i32> {
let mut ans = Vec::new();
fn dfs(node: Option<Rc<RefCell<TreeNode>>>, depth: usize, ans: &mut Vec<i32>) {
if let Some(node_ref) = node {
let node = node_ref.borrow();
if ans.len() == depth {
ans.push(node.val);
}
dfs(node.right.clone(), depth + 1, ans);
dfs(node.left.clone(), depth + 1, ans);
}
}
dfs(root, 0, &mut ans);
ans
}
}
```

#### JavaScript

```js
/**
* Definition for a binary tree node.
* function TreeNode(val, left, right) {
* this.val = (val===undefined ? 0 : val)
* this.left = (left===undefined ? null : left)
* this.right = (right===undefined ? null : right)
* }
*/
/**
* @param {TreeNode} root
* @return {number[]}
*/
var rightSideView = function (root) {
const ans = [];
const dfs = (root, depth) => {
if (!root) {
return;
}
if (ans.length == depth) {
ans.push(root.val);
}
dfs(root.right, depth + 1);
dfs(root.left, depth + 1);
};
dfs(root, 0);
return ans;
};
```

<!-- tabs:end -->

<!-- solution:end -->
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