Find Kth Largest Integer in the Array

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You are given an array of strings nums (representing non-negative integers) and integer k. Return the kth largest integer in nums (as a string). Compare by numeric value.

Example 1
Input: nums=["3","6","7","10"], k=4 → Output: "3"
Example 2
Input: nums=["2","21","12","1"], k=3 → Output: "2"

Solution Approach

Use a min-heap of size k (comparing by numeric string length then lexicographically). The top element is the kth largest.

  • Use a min-heap with comparator: compare by string length first, then lexicographically.
  • Add each string to heap; if size > k, poll minimum.
  • Return heap.peek().
Java
import java.util.*;

class Solution {
    public String kthLargestNumber(String[] nums, int k) {
        PriorityQueue<String> minHeap = new PriorityQueue<>((a, b) ->
            a.length() != b.length() ? a.length() - b.length() : a.compareTo(b));
        for (String n : nums) {
            minHeap.offer(n);
            if (minHeap.size() > k) minHeap.poll();
        }
        return minHeap.peek();
    }
}
  • Time Complexity: O(N log k)
  • Space Complexity: O(k)