Skip to content

feat: add solutions to lc problem: No.0742 #2724

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
May 6, 2024
Merged

feat: add solutions to lc problem: No.0742 #2724

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
147 changes: 75 additions & 72 deletions solution/0700-0799/0742.Closest Leaf in a Binary Tree/README.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -57,7 +57,11 @@

## 解法

### 方法一
### 方法一：DFS + BFS

我们首先使用深度优先搜索构建一个无向图 $g$，其中 $g[node]$ 表示与节点 $node$ 相邻的节点集合。然后我们从节点 $k$ 开始进行广度优先搜索，直到找到一个叶节点为止，即为答案。

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。

<!-- tabs:start -->

Expand All @@ -69,27 +73,27 @@
# self.left = left
# self.right = right
class Solution:
def findClosestLeaf(self, root: TreeNode, k: int) -> int:
def dfs(root, p):
def findClosestLeaf(self, root: Optional[TreeNode], k: int) -> int:
def dfs(root: Optional[TreeNode], fa: Optional[TreeNode]):
if root:
g[root].append(p)
g[p].append(root)
g[root].append(fa)
g[fa].append(root)
dfs(root.left, root)
dfs(root.right, root)

g = defaultdict(list)
dfs(root, None)
q = deque([node for node in g if node and node.val == k])
seen = set()
while q:
q = deque(node for node in g if node and node.val == k)
vis = set(q)
while 1:
node = q.popleft()
seen.add(node)
if node:
if node.left is None and node.right is None:
if node.left == node.right:
return node.val
for next in g[node]:
if next not in seen:
q.append(next)
for nxt in g[node]:
if nxt not in vis:
vis.add(nxt)
q.append(nxt)
```

```java
Expand All @@ -109,40 +113,38 @@ class Solution:
* }
*/
class Solution {
private Map<TreeNode, List<TreeNode>> g;
private Map<TreeNode, List<TreeNode>> g = new HashMap<>();

public int findClosestLeaf(TreeNode root, int k) {
g = new HashMap<>();
dfs(root, null);
Deque<TreeNode> q = new LinkedList<>();
for (Map.Entry<TreeNode, List<TreeNode>> entry : g.entrySet()) {
if (entry.getKey() != null && entry.getKey().val == k) {
q.offer(entry.getKey());
Set<TreeNode> vis = new HashSet<>(q.size());
for (TreeNode node : g.keySet()) {
if (node != null && node.val == k) {
vis.add(node);
q.offer(node);
break;
}
}
Set<TreeNode> seen = new HashSet<>();
while (!q.isEmpty()) {
while (true) {
TreeNode node = q.poll();
seen.add(node);
if (node != null) {
if (node.left == null && node.right == null) {
if (node.left == node.right) {
return node.val;
}
for (TreeNode next : g.get(node)) {
if (!seen.contains(next)) {
q.offer(next);
for (TreeNode nxt : g.get(node)) {
if (vis.add(nxt)) {
q.offer(nxt);
}
}
}
}
return 0;
}

private void dfs(TreeNode root, TreeNode p) {
private void dfs(TreeNode root, TreeNode fa) {
if (root != null) {
g.computeIfAbsent(root, k -> new ArrayList<>()).add(p);
g.computeIfAbsent(p, k -> new ArrayList<>()).add(root);
g.computeIfAbsent(root, k -> new ArrayList<>()).add(fa);
g.computeIfAbsent(fa, k -> new ArrayList<>()).add(root);
dfs(root.left, root);
dfs(root.right, root);
}
Expand All @@ -164,39 +166,41 @@ class Solution {
*/
class Solution {
public:
unordered_map<TreeNode*, vector<TreeNode*>> g;

int findClosestLeaf(TreeNode* root, int k) {
unordered_map<TreeNode*, vector<TreeNode*>> g;
function<void(TreeNode*, TreeNode*)> dfs = [&](TreeNode* root, TreeNode* fa) {
if (root) {
g[root].push_back(fa);
g[fa].push_back(root);
dfs(root->left, root);
dfs(root->right, root);
}
};
dfs(root, nullptr);
queue<TreeNode*> q;
for (auto& e : g) {
if (e.first && e.first->val == k) {
q.push(e.first);
break;
unordered_set<TreeNode*> vis;
for (auto& [node, _] : g) {
if (node && node->val == k) {
q.push(node);
vis.insert(node);
}
}
unordered_set<TreeNode*> seen;
while (!q.empty()) {
while (1) {
auto node = q.front();
q.pop();
seen.insert(node);
if (node) {
if (!node->left && !node->right) return node->val;
for (auto next : g[node]) {
if (!seen.count(next))
q.push(next);
if (node->left == node->right) {
return node->val;
}
for (auto& nxt : g[node]) {
if (vis.count(nxt)) {
continue;
}
q.push(nxt);
vis.insert(nxt);
}
}
}
return 0;
}

void dfs(TreeNode* root, TreeNode* p) {
if (!root) return;
g[root].push_back(p);
g[p].push_back(root);
dfs(root->left, root);
dfs(root->right, root);
}
};
```
Expand All @@ -211,42 +215,41 @@ public:
* }
*/
func findClosestLeaf(root *TreeNode, k int) int {
g := make(map[*TreeNode][]*TreeNode)
var dfs func(root, p *TreeNode)
dfs = func(root, p *TreeNode) {
if root == nil {
return
g := map[*TreeNode][]*TreeNode{}
var dfs func(*TreeNode, *TreeNode)
dfs = func(root, fa *TreeNode) {
if root != nil {
g[root] = append(g[root], fa)
g[fa] = append(g[fa], root)
dfs(root.Left, root)
dfs(root.Right, root)
}
g[root] = append(g[root], p)
g[p] = append(g[p], root)
dfs(root.Left, root)
dfs(root.Right, root)
}
dfs(root, nil)
var q []*TreeNode
for t, _ := range g {
if t != nil && t.Val == k {
q = append(q, t)
q := []*TreeNode{}
vis := map[*TreeNode]bool{}
for node := range g {
if node != nil && node.Val == k {
q = append(q, node)
vis[node] = true
break
}
}
seen := make(map[*TreeNode]bool)
for len(q) > 0 {
for {
node := q[0]
q = q[1:]
seen[node] = true
if node != nil {
if node.Left == nil && node.Right == nil {
if node.Left == node.Right {
return node.Val
}
for _, next := range g[node] {
if !seen[next] {
q = append(q, next)
for _, nxt := range g[node] {
if !vis[nxt] {
vis[nxt] = true
q = append(q, nxt)
}
}
}
}
return 0
}
```

Expand Down
Loading