41 lines
835 B
C++
41 lines
835 B
C++
#include <functional>
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#include <queue>
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#include <vector>
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#include <algorithm>
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struct TreeNode {
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int val;
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TreeNode* left;
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TreeNode* right;
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explicit TreeNode(int x = 0, TreeNode* l = nullptr, TreeNode* r = nullptr) : val(x), left(l), right(r) {}
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};
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class Solution {
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private:
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static int priorityQueue(TreeNode* root, int k) {
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std::vector<int> val;
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std::function<void(TreeNode*)> f = [&](TreeNode* ptr) {
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if (!ptr) return;
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val.push_back(ptr->val);
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if (ptr->left) f(ptr->left);
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if (ptr->right) f(ptr->right);
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};
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// O(n）
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f(root);
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// O(n)
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std::priority_queue<int, std::vector<int>, std::greater<>> q(val.begin(), val.end());
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// O(k * log(n))
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for (int i = 1; i < k; ++i)
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q.pop();
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return q.top();
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}
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public:
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static int kthSmallest(TreeNode* root, int k) {
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return priorityQueue(root, k);
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}
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};
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