865. Smallest Subtree with all the Deepest Nodes
Given the root of a binary tree, the depth of each node is the shortest distance to the root.
Return the smallest subtree such that it contains all the deepest nodes in the original tree.
A node is called the deepest if it has the largest depth possible among any node in the entire tree.
The subtree of a node is a tree consisting of that node, plus the set of all descendants of that node.
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class Solution {
public:
TreeNode* subtreeWithAllDeepest(TreeNode* root) {
if(!root) return root;
if(!root->right and !root->left) return root;
unordered_map<TreeNode*, TreeNode*> parentMap;
queue<TreeNode*> q;
unordered_set<TreeNode*> deepNodes{root};
q.push(root);
while(!q.empty()) {
int sz = q.size();
unordered_set<TreeNode*> temp;
while(sz--) {
auto n = q.front();
q.pop();
if(n->left) {
parentMap[n->left] = n;
temp.insert(n->left);
q.push(n->left);
}
if(n->right) {
parentMap[n->right] = n;
temp.insert(n->right);
q.push(n->right);
}
}
if(!temp.empty()) swap(deepNodes, temp);
}
while(deepNodes.size() != 1) {
unordered_set<TreeNode*> parentNode;
for(auto n : deepNodes) {
parentNode.insert(parentMap[n]);
}
swap(parentNode, deepNodes);
}
return *deepNodes.begin();
}
};
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class Solution {
pair<int, TreeNode*> findDeep(TreeNode* node, int depth) {
if(!node) return {0, node};
auto l = findDeep(node->left, depth + 1), r = findDeep(node->right, depth + 1);
return {max(l.first, r.first) + 1, l.first == r.first ? node : l.first > r.first ? l.second : r.second};
}
public:
TreeNode* subtreeWithAllDeepest(TreeNode* root) {
return findDeep(root, 0).second;
}
};
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