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The problem is to find the kth distinct string in an array. A distinct string is a string that appears exactly once in the array. You need to return the kth distinct string in the array. If there are fewer than k distinct strings, return an empty string "".

Example:

Input: arr = ["d","b","c","b","c","a"], k = 2
Output: "a"
Explanation: The only distinct strings in the array are "d" and "a". Return "a" since it is the 2nd distinct string.

Clarifying Questions

  1. Input Constraints:
    • What is the range of the length of the input array arr?
    • What is the maximum length of each string in the array?
    • What characters can the strings in the array have (e.g., only lowercase English letters)?

    Assumptions based on common LeetCode constraints:

    - The length of `arr` is in the range [1, 1000].
- Each string in `arr` has a length in the range [1, 100].
- The strings consist of lowercase English letters.
  2. Output:
    • If there are fewer than k distinct strings, return "".
  3. Edge Cases:
    • What if k is larger than the number of distinct strings?
    • What if arr has only one element?

Strategy

To solve this problem, we can use the following strategy:

  1. Count Occurrences: First, use a dictionary to count the occurrence of each string in the array.
  2. Collect Distinct Strings: Iterate through the array and collect strings that appear exactly once in the order they first appear.
  3. Find the kth Distinct: Return the kth distinct string if it exists; otherwise, return an empty string.

Code

def kthDistinct(arr, k):
    count = {}
    
    # Count the occurrences of each string
    for string in arr:
        if string in count:
            count[string] += 1
        else:
            count[string] = 1
            
    # Collect the distinct strings
    distinct_strings = [string for string in arr if count[string] == 1]
    
    # Return the kth distinct string (1-indexed)
    if k <= len(distinct_strings):
        return distinct_strings[k - 1]
    
    return ""

# Example usage:
arr = ["d", "b", "c", "b", "c", "a"]
k = 2
print(kthDistinct(arr, k))  # Output: "a"

Time Complexity

This approach ensures that we efficiently find the kth distinct string with clear steps and meets the problem requirements.

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