LeetCode 2537: Count the Number of Good Subarrays Solution
Master LeetCode problem 2537 (Count the Number of Good Subarrays), a medium 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.
2537. Count the Number of Good Subarrays
Problem Explanation
Explanation:
To solve this problem, we can use a sliding window approach along with prefix sums to efficiently count the number of good subarrays. We iterate through the array while maintaining a window of elements such that the number of matching pairs within the window is at least k. By keeping track of the frequency of each element in the window using a HashMap, we can determine the number of pairs within the window.
Algorithmic Idea:
- Initialize variables: count (to store the number of good subarrays), prefixSum (to store the prefix sum of the array elements), windowStart (start of the window), and a HashMap to keep track of the frequencies of elements in the window.
- Iterate through the array:
- Update the prefix sum at the current index.
- Calculate the number of pairs within the window by subtracting the prefix sum at the current index by k and check if the count of this value exists in the HashMap. If it does, increment count by the count of that value in the HashMap.
- Increment the count of the current prefix sum in the HashMap.
- Return the final count.
Time Complexity:
The time complexity of this solution is O(n), where n is the length of the input array nums.
Space Complexity:
The space complexity of this solution is O(n) to store the prefix sum and the HashMap.
:
Solution Code
class Solution {
public int numberOfSubarrays(int[] nums, int k) {
int count = 0;
int prefixSum = 0;
int windowStart = 0;
Map<Integer, Integer> freqMap = new HashMap<>();
freqMap.put(0, 1);
for (int num : nums) {
prefixSum += num;
if (freqMap.containsKey(prefixSum - k)) {
count += freqMap.get(prefixSum - k);
}
freqMap.put(prefixSum, freqMap.getOrDefault(prefixSum, 0) + 1);
}
return count;
}
}Try It Yourself
Loading code editor...
Related LeetCode Problems
Frequently Asked Questions
How to solve LeetCode 2537 (Count the Number of Good Subarrays)?
This page provides optimized solutions for LeetCode problem 2537 (Count the Number of Good Subarrays) in Java, C++, and Python, along with a detailed explanation and an interactive code editor to test your code.
What is the time complexity of LeetCode 2537 (Count the Number of Good Subarrays)?
The time complexity for LeetCode 2537 (Count the Number of Good Subarrays) varies by solution. Check the detailed explanation section for specific complexities in Java, C++, and Python implementations.
Can I run code for LeetCode 2537 on DevExCode?
Yes, DevExCode provides an interactive code editor where you can write, test, and run your code for LeetCode 2537 in Java, C++, or Python.