LeetCode 2190: Most Frequent Number Following Key In an Array Solution

Master LeetCode problem 2190 (Most Frequent Number Following Key In an Array), a easy challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

2190. Most Frequent Number Following Key In an Array

Easy

Array Hash Table Counting

Problem Explanation

Explanation

To solve this problem, we will iterate through the given array nums and count occurrences of the target number following the key. We can achieve this by keeping track of the count of each target following the key in a hashmap. We increment the count whenever we find a target following the key. Finally, we return the target with the maximum count.

We will initialize a hashmap to store counts of targets following the key.
We iterate through the array and increment the count for the target following the key.
After iterating through the array, we find the target with the maximum count.

Time Complexity: O(n) where n is the length of the input array nums. Space Complexity: O(n) for the hashmap to store counts.

Solution Code

class Solution {
    public int findMostFrequentNumberFollowingKey(int[] nums, int key) {
        Map<Integer, Integer> countMap = new HashMap<>();
        
        for (int i = 0; i < nums.length - 1; i++) {
            if (nums[i] == key) {
                int target = nums[i + 1];
                countMap.put(target, countMap.getOrDefault(target, 0) + 1);
            }
        }
        
        int maxCount = 0;
        int result = -1;
        for (Map.Entry<Integer, Integer> entry : countMap.entrySet()) {
            if (entry.getValue() > maxCount) {
                maxCount = entry.getValue();
                result = entry.getKey();
            }
        }
        
        return result;
    }
}

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