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| 1 | +def binary_search_2d(matrix: list[list[int]], target: int) -> tuple[int, int]: |
| 2 | + """ |
| 3 | + Searches for a target value in a 2D sorted array. |
| 4 | +
|
| 5 | + The matrix is sorted such that each row is in ascending order, and the |
| 6 | + first element of each row is greater than the last element of the previous row. |
| 7 | +
|
| 8 | + :param matrix: A 2D list of integers sorted in ascending order. |
| 9 | + :param target: The integer value to search for. |
| 10 | + :return: A tuple (row_index, col_index) if found, otherwise (-1, -1). |
| 11 | +
|
| 12 | + Examples: |
| 13 | + >>> binary_search_2d([[1, 3, 5], [7, 9, 11], [12, 13, 15]], 9) |
| 14 | + (1, 1) |
| 15 | + >>> binary_search_2d([[1, 3, 5], [7, 9, 11], [12, 13, 15]], 4) |
| 16 | + (-1, -1) |
| 17 | + """ |
| 18 | + if not matrix or not matrix[0]: |
| 19 | + return -1, -1 |
| 20 | + |
| 21 | + rows, cols = len(matrix), len(matrix[0]) |
| 22 | + left, right = 0, rows * cols - 1 |
| 23 | + |
| 24 | + while left <= right: |
| 25 | + mid = left + (right - left) // 2 |
| 26 | + mid_value = matrix[mid // cols][mid % cols] |
| 27 | + |
| 28 | + if mid_value == target: |
| 29 | + return mid // cols, mid % cols |
| 30 | + elif mid_value < target: |
| 31 | + left = mid + 1 |
| 32 | + else: |
| 33 | + right = mid - 1 |
| 34 | + |
| 35 | + return -1, -1 |
| 36 | + |
| 37 | + |
| 38 | +if __name__ == "__main__": |
| 39 | + import doctest |
| 40 | + |
| 41 | + doctest.testmod() |
| 42 | + |
| 43 | + # Example usage |
| 44 | + matrix = [[1, 3, 5], [7, 9, 11], [12, 13, 15]] |
| 45 | + target = 9 |
| 46 | + result = binary_search_2d(matrix, target) |
| 47 | + if result == (-1, -1): |
| 48 | + print(f"{target} was not found in the matrix.") |
| 49 | + else: |
| 50 | + print(f"{target} was found at position {result} in the matrix.") |
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