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| 1 | +# Leetcode Daily Challenge Solutions |
| 2 | + |
| 3 | +## Today's 31-03-24 [Problem Link](https://leetcode.com/problems/count-subarrays-with-fixed-bounds/description/?envType=daily-question&envId=2024-03-31) |
| 4 | +## 2444. Count Subarrays With Fixed Bounds |
| 5 | + |
| 6 | +# Intuition |
| 7 | +<!-- Describe your first thoughts on how to solve this problem. --> |
| 8 | +The problem requires counting the number of subarrays within a given range [minK, maxK] where the subarray's elements are also within this range. To efficiently count these subarrays, I can iterate through the array once and keep track of the last invalid index, the last occurrence of minK, and the last occurrence of maxK. By doing so, I can determine the valid subarrays that end at each index. |
| 9 | + |
| 10 | +# Approach |
| 11 | +<!-- Describe your approach to solving the problem. --> |
| 12 | + |
| 13 | +- Initialized variables : |
| 14 | +- `count`: to store the count of valid subarrays. |
| 15 | +- `lastInvalidIndex`: to keep track of the index of the last element that violates the range condition. |
| 16 | +- `lastMinIndex`: to store the index of the last occurrence of minK. |
| 17 | +- `lastMaxIndex`: to store the index of the last occurrence of maxK. |
| 18 | + |
| 19 | +- Iterated through the array `nums` : |
| 20 | +- Updated `lastInvalidIndex` if the current element is out of the range [minK, maxK]. |
| 21 | +- Updated `lastMinIndex` if the current element is equal to minK. |
| 22 | +- Updated `lastMaxIndex` if the current element is equal to maxK. |
| 23 | +- Calculated the count of valid subarrays up to the current index by taking the maximum of 0 and the difference between the minimum of `lastMinIndex` and `lastMaxIndex` and `lastInvalidIndex`. |
| 24 | +- Added this count to the `count`. |
| 25 | + |
| 26 | +- Returned the total count of valid subarrays. |
| 27 | + |
| 28 | +By following this approach, I can efficiently count the number of valid subarrays within the given range. |
| 29 | + |
| 30 | +--- |
| 31 | +Have a look at the code , still have any confusion then please let me know in the comments |
| 32 | +Keep Solving.:) |
| 33 | +# Complexity |
| 34 | +- Time complexity : $O(n)$ |
| 35 | +<!-- Add your time complexity here, e.g. $$O(n)$$ --> |
| 36 | +$n$ : length of the input array `nums` |
| 37 | +- Space complexity : $O(1)$ |
| 38 | +<!-- Add your space complexity here, e.g. $$O(n)$$ --> |
| 39 | + |
| 40 | +# Code |
| 41 | +``` |
| 42 | +class Solution { |
| 43 | +
|
| 44 | +// Function to count subarrays within the given range [minK, maxK] |
| 45 | +public long countSubarrays(int[] nums, int minK, int maxK) { |
| 46 | +
|
| 47 | +// Variable to store the count of valid subarrays |
| 48 | +long count = 0; |
| 49 | +// Index of the last element that violates the range condition |
| 50 | +int lastInvalidIndex = -1; |
| 51 | +// Index of the last occurrence of minK |
| 52 | +int lastMinIndex = -1; |
| 53 | +// Index of the last occurrence of maxK |
| 54 | +int lastMaxIndex = -1; |
| 55 | +
|
| 56 | +// Iterating through the array |
| 57 | +for (int i = 0; i < nums.length; ++i) { |
| 58 | +// Updating lastInvalidIndex if current element is out of range |
| 59 | +if (nums[i] < minK || nums[i] > maxK) { |
| 60 | +lastInvalidIndex = i; |
| 61 | +} |
| 62 | +// Updating lastMinIndex if current element is equal to minK |
| 63 | +if (nums[i] == minK) { |
| 64 | +lastMinIndex = i; |
| 65 | +} |
| 66 | +// Updating lastMaxIndex if current element is equal to maxK |
| 67 | +if (nums[i] == maxK) { |
| 68 | +lastMaxIndex = i; |
| 69 | +} |
| 70 | +// Calculating the count of valid subarrays up to the current index |
| 71 | +count += Math.max(0, Math.min(lastMinIndex, lastMaxIndex) - lastInvalidIndex); |
| 72 | +} |
| 73 | +// Returning the total count of valid subarrays |
| 74 | +return count; |
| 75 | +} |
| 76 | +} |
| 77 | +``` |
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