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39 lines
1.0 KiB
39 lines
1.0 KiB
/**
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* File: top_k.cpp
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* Created Time: 2023-06-12
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* Author: krahets (krahets@163.com)
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*/
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#include "../utils/common.hpp"
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/* 基於堆積查詢陣列中最大的 k 個元素 */
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priority_queue<int, vector<int>, greater<int>> topKHeap(vector<int> &nums, int k) {
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// 初始化小頂堆積
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priority_queue<int, vector<int>, greater<int>> heap;
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// 將陣列的前 k 個元素入堆積
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for (int i = 0; i < k; i++) {
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heap.push(nums[i]);
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}
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// 從第 k+1 個元素開始，保持堆積的長度為 k
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for (int i = k; i < nums.size(); i++) {
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// 若當前元素大於堆積頂元素，則將堆積頂元素出堆積、當前元素入堆積
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if (nums[i] > heap.top()) {
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heap.pop();
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heap.push(nums[i]);
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}
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}
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return heap;
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}
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// Driver Code
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int main() {
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vector<int> nums = {1, 7, 6, 3, 2};
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int k = 3;
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priority_queue<int, vector<int>, greater<int>> res = topKHeap(nums, k);
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cout << "最大的 " << k << " 個元素為: ";
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printHeap(res);
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return 0;
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}
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