📌 이진 힙 구현
✔ 파이썬의 heapq 모듈에서 지원하는 최소 힙 연산을 파이썬의 리스트만으로 동일하게 구현
class BinaryHeap:
def __init__(self):
self.items = [None]
def __len__(self):
return len(self.items) - 1
def _percolate_up(self):
idx = len(self)
parent = idx // 2
while parent and self.items[idx] < self.items[parent]:
self.items[idx], self.items[parent] = self.items[parent], self.items[idx]
idx = parent
parent = idx // 2
def insert(self, data):
self.items.append(data)
self._percolate_up()
def _percolate_down(self, idx):
left = idx * 2
right = idx * 2 + 1
smallest = idx
if left <= len(self) and self.items[left] < self.items[smallest]:
smallest = left
if right <= len(self) and self.items[right] < self.items[smallest]:
smallest = right
if smallest != idx:
self.items[smallest], self.items[idx] = self.items[idx], self.items[smallest]
return self._percolate_down(smallest)
def extract(self):
extracted = self.items[1]
self.items[1] = self.items.pop()
self._percolate_down(1)
return extracted
if __name__ == '__main__':
binary_heap = BinaryHeap()
binary_heap.insert(16)
print(binary_heap.items)
binary_heap.insert(10)
print(binary_heap.items)
binary_heap.insert(14)
print(binary_heap.items)
binary_heap.insert(2)
print(binary_heap.items)
binary_heap.insert(4)
print(binary_heap.items)
binary_heap.insert(1)
print(binary_heap.items)
binary_heap.insert(8)
print(binary_heap.items)
binary_heap.insert(7)
print(binary_heap.items)
binary_heap.insert(9)
print(binary_heap.items)
binary_heap.insert(3)
print(binary_heap.items)
binary_heap.insert(3)
print(binary_heap.items)
print(binary_heap.extract())
print(binary_heap.items)
print(binary_heap.extract())
print(binary_heap.items)
print(binary_heap.extract())
print(binary_heap.items)
print(binary_heap.extract())
print(binary_heap.items)
print(binary_heap.extract())
print(binary_heap.items)
✔ 풀이1 (heapq모듈 이용)
import heapq
class Solution:
def findKthLargest(self, nums: List[int], k: int) -> int:
hq = []
for n in nums:
heapq.heappush(hq, -n)
for i in range(1, k):
heapq.heappop(hq)
return -heapq.heappop(hq)
✔ 풀이2 (heapq모듈의 heapify 이용)
import heapq
class Solution:
def findKthLargest(self, nums: List[int], k: int) -> int:
heapq.heapify(nums)
for i in range(len(nums) - k):
heapq.heappop(nums)
return heapq.heappop(nums)
✔ 풀이3 (heapq모듈의 nlargest 이용)
import heapq
class Solution:
def findKthLargest(self, nums: List[int], k: int) -> int:
return heapq.nlargest(k, nums)[-1]
✔ 풀이4 (정렬을 이용한 이용)
class Solution:
def findKthLargest(self, nums: List[int], k: int) -> int:
nums.sort()
return nums[-k]