Top 20 Heap and Priority Queue Interview Questions (2026)

1. Introduction to Heaps

Heaps provide O(1) peek and O(log n) insertion/deletion for priority management. Below are 20 essential questions with complete solutions in C++, Java, Python, and JavaScript.

2. Core Heap Questions

Q1. Kth Largest Element in an Array

cpp
int findKthLargest(vector<int>& nums, int k) {
    priority_queue<int, vector<int>, greater<int>> minHeap;
    for (int num : nums) {
        minHeap.push(num);
        if (minHeap.size() > k) minHeap.pop();
    }
    return minHeap.top();
}

java
public int findKthLargest(int[] nums, int k) {
    PriorityQueue<Integer> minHeap = new PriorityQueue<>();
    for (int num : nums) {
        minHeap.add(num);
        if (minHeap.size() > k) minHeap.poll();
    }
    return minHeap.peek();
}

python
import heapq
def findKthLargest(nums: list, k: int) -> int:
    min_heap = []
    for num in nums:
        heapq.heappush(min_heap, num)
        if len(min_heap) > k:
            heapq.heappop(min_heap)
    return min_heap[0]

javascript
function findKthLargest(nums, k) {
    nums.sort((a, b) => b - a);
    return nums[k - 1];
}

Time Complexity: O(n log k) | Space Complexity: O(k)

3. Summary Table

Practice all heap problems on DSAMaster's practice platform.