The puzzle consists of the grid 9x9 and 3x3 box. In some regions, the numeral is given in the grid. The objective is to fill one digit in blank cells in each row and column contains the digit 1-9 without repeating number. So the word single number occurs from this puzzle.

        Conclusion

           The strategy for solving a puzzle consists of three processes: scanning, marking up and analyzing.

Scanning is performed at the outset and throughout the solution. Scans need to be performed only once in between analysis. Scanning consists of two techniques: 1. Cross-hatcing the scanning of rows and columns to identify which line in region may contain a certain numeral by a process of elimination. For fastest results, the numerals are scanned in order of their frequency (from high to low) and check all of the digits 1-9. 2. Counting 1 – 9 counting in rows and columns to identify missing numerals. Counting based on the last numeral discovered may speed up the search. The best way to ascertain the value of a cell is to count in reverse. On the other hand (particular in tougher puzzles), scanning the value in cell's region in row and column in order to see what remains.

Scanning stops when no further numerals can be found. One method to guide the analysis is to mark candidate numerals in the blank cells. There are two popular methods are subscripts and dots. In Subscript notation the candidate numerals are written in subscript in the cells. Because puzzles printed in a newspaper are too small to accommodate more than a few subscript digits of normal handwriting. Solvers may create a larger copy of the puzzle. The second notation uses a pattern of dots in each square, where the dot position indicates a number from 1 to 9 that is useful for puzzle. Dexterity is required in placing the dots, misplaced dots or inadvertent marks lead to confusion so using pencil to place dots is better.

There are 2 main approaches to analyze are “Candidate elimination” and “What-if”. - Candidate elimination is made by successively eliminating candidate numerals from cells to leave one choice. After each answer has been added into cell, another scan may be performed to check and see the effect of the contingencies and eliminating irrelevant numbers. - What-if approach, a cell with two candidate numerals is selected and a guess is made. The steps are repeated unless duplication is found or a cell is left without a possible candidate in which are the alternative candidate must be the solution.

In set of digits 1 to 9, assumed the last cell should be. This approach is the way to check the digit into the cell after the grid has given some numerals. In each set eliminating the duplicate number.

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