leetcode 703. Kth Largest Element in a Stream（python）

描述

Design a class to find the kth largest element in a stream. Note that it is the kth largest element in the sorted order, not the kth distinct element.

Implement KthLargest class:

• KthLargest(int k, int[] nums) Initializes the object with the integer k and the stream of integers nums.
• int add(int val) Returns the element representing the kth largest element in the stream.

Example 1:

Input
["KthLargest", "add", "add", "add", "add", "add"]
[[3, [4, 5, 8, 2]], [3], [5], [10], [9], [4]]
Output
[null, 4, 5, 5, 8, 8]

Explanation
KthLargest kthLargest = new KthLargest(3, [4, 5, 8, 2]);
kthLargest.add(3);   // return 4
kthLargest.add(5);   // return 5
kthLargest.add(10);  // return 5
kthLargest.add(9);   // return 8
kthLargest.add(4);   // return 8

Note:

• 1 <= k <= 104
• 0 <= nums.length <= 104
• -104 <= nums[i] <= 104
• -104 <= val <= 104
• At most 104 calls will be made to add.
• It is guaranteed that there will be at least k elements in the array when you search for the kth element.

解析

根据题意，只需要每次在 nums 加入新的元素 val 之后，重新排序，得到 Kth 的值即可，解答很简单但是因为提交之后可能有上万次的 add() 过程，所以会很耗时，所以用到了堆排序节省时间。

解答

class KthLargest(object):

    def __init__(self, k, nums):
        """
        :type k: int
        :type nums: List[int]
        """
        self.k = k
        self.nums = nums

    def add(self, val):
        """
        :type val: int
        :rtype: int
        """
        self.nums.append(val)
        self.nums.sort()
        return self.nums[-self.k]

运行结果

Runtime: 1088 ms, faster than 16.64% of Python online submissions for Kth Largest Element in a Stream.
Memory Usage: 18 MB, less than 10.91% of Python online submissions for Kth Largest Element in a Stream.

解答

class KthLargest(object):

    def __init__(self, k, nums):
        """
        :type k: int
        :type nums: List[int]
        """
        self.k = k
        self.nums = nums
        heapify(self.nums)
        while len(self.nums) > self.k:
            heappop(self.nums)

    def add(self, val):
        """
        :type val: int
        :rtype: int
        """
        if len( self.nums ) < self.k:
            heappush(self.nums, val)
        else:
            heappushpop(self.nums, val)
        return self.nums[0]

运行结果

Runtime: 88 ms, faster than 96.49% of Python online submissions for Kth Largest Element in a Stream.
Memory Usage: 17.7 MB, less than 92.79% of Python online submissions for Kth Largest Element in a Stream.

原题链接：https://leetcode.com/problems/kth-largest-element-in-a-stream/