sudoku locked candidate

Sudoku Locked Candidate Strategy: A Comprehensive Guide to Solve Puzzles

Sudoku, the popular logic-based number-placement puzzle, has captured the interest of puzzle enthusiasts worldwide. One of the most effective strategies used in solving Sudoku is the "Locked Candidate" technique. This article delves into the details of the Locked Candidate strategy, providing you with a comprehensive guide to master this powerful tool.

Understanding the Concept

The Locked Candidate, also known as "Pointing Pair" or "Box Line Reducation," is a technique that simplifies the Sudoku solving process by identifying numbers that can only be placed in specific cells within a row, column, or block.

Identifying a Locked Candidate

To identify a Locked Candidate, follow these steps:

1. Scan Rows and Columns: Look for pairs of numbers in the same row or column that appear twice in the same box. These pairs are your candidates.
2. Check the Boxes: Determine if these candidates can only be placed in the cells that are not already occupied by other numbers in their respective boxes.

Applying the Technique

Once you've identified a Locked Candidate, here’s how to apply the technique:

1. Eliminate: Cross out all other cells in the row, column, or box where the candidates can be placed, as they cannot contain those numbers.
2. Recheck: After making eliminations, recheck your work to ensure that no other candidates have been missed.

Example

Consider a Sudoku puzzle where the numbers 1 and 4 appear twice in the same box, and only in cells within a single row and column. If these cells are also the only places in the box where the numbers 1 and 4 can be placed, you have a Locked Candidate.

1. Identify: Notice that the numbers 1 and 4 can only be placed in two cells of the row and column, which are part of the same box.
2. Eliminate: Cross out all other cells in the row and column where the numbers 1 and 4 can be placed.
3. Solve: Now, you can place the numbers 1 and 4 in the remaining cells.

Tips for Effective Use

• Patience: The Locked Candidate technique requires patience, as it can sometimes be time-consuming to identify.
• Practice: Regular practice will help you recognize patterns and improve your speed in applying the technique.
• Combine: Use the Locked Candidate in conjunction with other strategies to enhance your solving capabilities.

Conclusion

The Locked Candidate strategy is a valuable addition to your Sudoku solving toolkit. By identifying and eliminating potential candidates, you can simplify complex puzzles and increase your chances of solving them efficiently. Incorporate this technique into your regular practice, and watch your Sudoku-solving skills soar!