Complete Problem 6

[dhruvil15]

No description provided.

[super30admin]

Search inside a Rotated Sorted Array (Problem6.java)

Your solution is excellent! You have correctly implemented the binary search for a rotated sorted array. The code is clean, well-commented, and efficient. Here are a few points to consider for future improvements:

1. Consistency in Conditions: In the right half condition, you have target <= nums[right] && target > nums[mid]. This is correct, but note that the left half condition uses target >= nums[left] && target < nums[mid]. Both conditions are symmetric, which is good. However, you might consider using the same pattern (e.g., using inclusive checks for the boundaries) to maintain consistency. This is a minor point and does not affect correctness.

2. Edge Cases: Your solution handles edge cases (like a single element array) correctly because the while loop condition left <= right ensures that all elements are considered. This is good.

3. Comments: Your comments are helpful, but you could add a brief explanation at the top of the function about the overall strategy (e.g., "We use binary search by checking which half is sorted and then narrowing down the search based on whether the target is in the sorted half"). This would make the code even more understandable.

Overall, this is a solid implementation. Keep up the good work!

VERDICT: PASS

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Search Inside a Sorted Array whose Length is unknown

Strengths:

• Your code is well-commented and follows good coding practices.
• The logic for solving the rotated sorted array problem is correct and efficient.

Areas for Improvement:

• The problem you solved is different from the one described. The problem here is about an array with unknown length, where you need to use the ArrayReader interface. You must read the problem statement carefully to understand the requirements.
• You need to implement a solution that first finds the range where the target might exist by doubling the index until you exceed the target, and then perform binary search within that range.
• The ArrayReader interface is not used in your solution. Instead, you are given an array nums as input, which is not the case in this interactive problem.

Please revisit the problem statement and adjust your solution to use the ArrayReader interface. Here's a suggested approach:

1. Start with low = 0 and high = 1.
2. While ArrayReader.get(high) is less than the target, set low = high and high = high * 2. This will expand the search range exponentially.
3. Once you have a range where the target might be (i.e., when ArrayReader.get(high) >= target or the value is out of bounds), perform binary search between low and high.

VERDICT: NEEDS_IMPROVEMENT

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Search a 2D Matrix

Your solution is well-written for the problem of "Search in Rotated Sorted Array", but it does not solve the "Search a 2D Matrix" problem. The problem requires you to search in a 2D matrix where each row is sorted and the first integer of each row is greater than the last integer of the previous row. This means the entire matrix can be treated as a single sorted list of size m*n.

To solve this problem, you should use a binary search over the entire matrix by converting the 1D index to 2D indices. For example, if you have an m x n matrix, the total number of elements is mn. You can set low=0 and high=mn-1. Then, for each mid index, you can compute the row as mid/n and the column as mid%n. Then compare the element at matrix[row][column] with the target.

Here is a reference solution for your review:

class Solution {
    public boolean searchMatrix(int[][] matrix, int target) {
        int m = matrix.length;
        int n = matrix[0].length;
        int low = 0, high = m * n - 1;
        while (low <= high) {
            int mid = low + (high - low) / 2;
            int r = mid / n;
            int c = mid % n;
            if (matrix[r][c] == target) {
                return true;
            } else if (matrix[r][c] < target) {
                low = mid + 1;
            } else {
                high = mid - 1;
            }
        }
        return false;
    }
}

Please note that you must ensure the solution matches the problem statement. Always double-check the problem requirements before implementing.

VERDICT: NEEDS_IMPROVEMENT

[dhruvil15]

I've completed the problem7