Recall & Review
beginner
What is the main idea behind searching in a 2D matrix where each row and column is sorted?
Start from the top-right corner and move left if the current number is greater than the target, or move down if it is smaller. This way, you eliminate a row or a column each step.
Click to reveal answer
beginner
Why is starting from the top-right corner effective in a sorted 2D matrix search?
Because from the top-right corner, moving left decreases the value and moving down increases the value, helping to decide the direction to move based on comparison with the target.
Click to reveal answer
intermediate
What is the time complexity of searching in a sorted 2D matrix using the top-right corner approach?
O(m + n), where m is the number of rows and n is the number of columns, because each step moves either one row down or one column left.
Click to reveal answer
beginner
In the context of searching a 2D matrix, what does it mean if the current element is less than the target?
It means you should move down to the next row because all elements to the left are smaller and won't match the target.
Click to reveal answer
beginner
What happens if the target is not found after moving through the matrix using the top-right corner approach?
You conclude the target is not in the matrix because you have eliminated all possible positions by moving left or down.
Click to reveal answer
Where do you start searching in a sorted 2D matrix to efficiently find a target?
✗ Incorrect
Starting at the top-right corner allows you to move left or down to eliminate rows or columns efficiently.
If the current element is greater than the target, what is the next move?
✗ Incorrect
Moving left decreases the value, helping to find smaller numbers closer to the target.
What is the time complexity of the search algorithm in a sorted 2D matrix?
✗ Incorrect
Each step moves either one row down or one column left, so the total steps are at most m + n.
If the current element is less than the target, where should you move next?
✗ Incorrect
Moving down increases the value, which helps to find the target if it is larger.
What does it mean if you reach outside the matrix boundaries without finding the target?
✗ Incorrect
Exiting the matrix means all possible positions have been checked and the target is not present.
Explain the step-by-step process to search for a target in a sorted 2D matrix.
Think about how to eliminate rows or columns based on comparison.
You got /5 concepts.
Describe why the search in a sorted 2D matrix is efficient compared to checking every element.
Focus on how sorting helps reduce search space.
You got /4 concepts.