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| #include <vector>
#include <iostream>
class Solution {
public:
std::vector<int> getLeastNumbers(std::vector<int>& arr, int k) {
if (arr.empty() || arr.size() < k || k <= 0) {
return std::vector<int>();
}
std::vector<int> heap(k, 0);
for (size_t i = 0; i < k; ++i) {
heap_insert(heap, arr[i], i);
}
for (size_t i = k; i < arr.size(); ++i) {
if (arr[i] < heap[0]) {
heap[0] = arr[i];
heapify(heap, 0, k);
}
}
return heap;
}
private:
void heap_insert(std::vector<int>& heap, int value, int index) {
heap[index] = value;
for (; index != 0;) {
int parent = (index - 1) / 2;
if (heap[parent] < heap[index]) {
std::swap(heap[parent], heap[index]);
index = parent;
} else {
break;
}
}
}
void heapify(std::vector<int>& heap, int index, int heap_size) {
int left = index * 2 + 1;
int right = index * 2 + 2;
int largest = index;
for (; left < heap_size;) {
if (heap[index] < heap[left]) {
largest = left;
}
if (right < heap_size && heap[right] > heap[largest]) {
largest = right;
}
if (largest != index) {
std::swap(heap[largest], heap[index]);
} else {
break;
}
index = largest;
left = index * 2 + 1;
right = index * 2 + 2;
}
}
};
void print_vec(const std::vector<int>& arr) {
for (const auto& x : arr) {
std::cout << x << " ";
}
std::cout << std::endl;
}
int main() {
std::vector<int> arr{0, 1, 1, 2, 4, 4, 1, 3, 3, 2};
Solution s;
auto res = s.getLeastNumbers(arr, 6);
print_vec(res);
return 0;
}
|