LeetCode 3034: Number of Subarrays That Match a Pattern I Solution

Master LeetCode problem 3034 (Number of Subarrays That Match a Pattern I), 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.

3034. Number of Subarrays That Match a Pattern I

Medium

Array Rolling Hash String Matching Hash Function

Problem Explanation

Explanation

To solve this problem, we can iterate through the nums array and check each subarray of size m+1 if it matches the given pattern. We compare each element of the subarray with the corresponding element of the pattern based on the rules provided. If all elements match the pattern, we increment a counter. Finally, we return the count of subarrays that match the pattern.

We iterate through the nums array.
For each index i, we check if nums[i..i+m] matches the pattern.
If a subarray matches the pattern, we increment the counter.
Finally, we return the count of matching subarrays.

Time complexity: O(n*m) where n is the length of nums and m is the length of the pattern. Space complexity: O(1)

Solution Code

class Solution {
    public int numOfSubarrays(int[] nums, int[] pattern) {
        int count = 0;
        int n = nums.length;
        int m = pattern.length;
        
        for (int i = 0; i <= n - m; i++) {
            if (matchesPattern(nums, pattern, i)) {
                count++;
            }
        }
        
        return count;
    }
    
    private boolean matchesPattern(int[] nums, int[] pattern, int start) {
        for (int k = 0; k < pattern.length; k++) {
            int diff = nums[start + k + 1] - nums[start + k];
            if ((pattern[k] == 1 && diff <= 0) ||
                (pattern[k] == 0 && diff != 0) ||
                (pattern[k] == -1 && diff >= 0)) {
                return false;
            }
        }
        return true;
    }
}

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