Créer une présentation
Télécharger la présentation

Télécharger la présentation
## Solving a Sudoku Puzzle

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -

**Solving a Sudoku Puzzle**By Marlene Walther**Rows go across …**• Use the numbers from 1 to 9 only! Each row has 9 cells across The numbers 1 to 9 will appear only once in each row There are 9 rows in a puzzle**Columns go down …**Each column has 9 cells down The numbers 1 to 9 will appear only once in each column There are 9 columns in each puzzle**Blocks …**The numbers 1-9 will appear only once in each 3 x 3 block There are 9 blocks in each puzzle**So …**We have 9 columns We have 9 rows And we have 9 blocks**Step #1**• Look at the three blocks on the left side of the puzzle Notice which numbers are repeated (1, 3, 4, 7) Notice that the number 3 is in Column 1 and Column 2**Step #1**• The number 3 can appear only once in each column The number 3 is already in Column 1 and Column 2, so where will it go in Column 3? The number 3 must appear in the bottom block because it is in the top two blocks already**Step #1**The number 3 cannot appear in any column or row where it is already The number 3 cannot appear in any block where it is already It must go here – the only place left**Step #1**• Write the number 3 in the cell 3**Step #2**• Look at the number 1 in the three blocks on the left • The number 1 cannot appear in those two columns again • The number 1 cannot appear in the top or bottom block 3 • There is only one cell in the third column where the number 1 can go. Can you find it?**Step #2**• Did you get it right? 1 3**Step #3**• Look at the number 4 in the first three blocks on the left • The number 4 cannot appear in those two columns or those two blocks again 1 • There is only one cell in the top block where the number 4 can go. • Can you find it? 3**Step #3**4 • Did you get it right? 1 3**Step #4**4 • Look at the number 7 in the middle three blocks • The number 7 cannot appear in those two columns again 1 • There is only one cell in the top middle block where the number 7 can go. • Can you find it? 3**Step #4**4 7 • Did you get it right? 1 3**Step #5**4 • Look at the number 7’s in the top three blocks and the blocks on the left 7 • The number 7 cannot appear in any row or column twice 1 • There is only one cell in the top block where the number 7 can go. • Can you find it? 3**Step #5**4 7 7 • Did you get it right? 1 3**Step #6**4 • Notice all the 7’s in the puzzle. 7 • There is one 7 in every block except the bottom right block 7 1 • There is only one cell where the number 7 can go. • Can you find it? 3**Step #6**4 • Did you get it right? 7 7 1 3 7**Step #7**4 7 • Where will the 4 go in this block? 7 1 • Would you like a hint? 3 7**Step #7**4 7 7 1 3 7**Step #7**4 • Did you get it right? 7 4 7 1 3 7**Step #8**4 • Fill in the number 4 in the bottom right block • It can only go in one cell 7 4 7 1 3 7**Step #8**4 7 4 7 • Did you get it right? 1 3 7 4**Step #9**4 • There is only one possible cell for the number 3 in the bottom right block • Where does the number 3 go? • Would you like a hint? 7 4 7 1 3 7 4**Step #9**4 7 4 7 • It can only go in one cell. • Can you find it? 1 3 7 4**Step #9**4 7 4 7 • Did you get it right? 1 3 7 3 4**Step #10**4 7 4 • Where will the number 3 go in the middle block? • Would you like a hint? 7 1 3 7 3 4**Step #10**4 7 4 7 • There is only one place for the number 3 in the middle block 1 3 7 3 4**Step #10**4 • Did you get it right? 7 4 7 1 3 3 7 3 4**Step #11**4 7 4 • Where will the number 3 go in the top middle block? • It can only go in one cell. 7 1 3 3 7 3 4**Step #11**4 7 3 4 7 1 3 • Did you get it right? 3 7 3 4**Step #12**4 • Can you figure out where the number 2 will go in the top left block? • Would you like a hint? 7 3 4 7 1 3 3 7 3 4**Step #12**4 7 3 4 7 • There is only one possible cell for the number 2 in the top left block. 1 3 3 7 3 4**Step #12**4 2 7 3 4 7 • Did you get it right? 1 3 3 7 3 4**Step #13**4 2 • There are only two cells open in the top middle block • You can use the numbers 1-9 only once in each block • Which two numbers must go in those two cells? 7 3 4 7 1 3 3 7 3 4**Step #13**4 2 • The numbers 2 and 9 must go in this block • There is only one place for the number 2 • Would you like a hint? 7 3 4 7 1 3 3 7 3 4**Step #13**• The number 2 cannot go in the top row because there is a 2 in that row • Therefore, 2 must go in the third row • And then the number 9 must go in the top row (the only cell left in that block) 4 2 7 3 4 7 1 3 3 7 3 4**Step #13**4 2 9 • You can now see that the top middle block has all the numbers from 1-9 in it • No number is repeated in that block 7 3 4 7 2 1 3 3 7 3 4**Step #14**4 2 9 3 • Where will the 3 go in the top right block? 7 3 4 7 2 1 3 • Did you get it right? 3 7 3 4**Step #15**4 2 9 3 • Where will the 5 go in the top left block? 7 3 4 7 5 2 1 3 • Did you get it right? 3 7 3 4**Step #16**4 2 9 3 • Where will the 9 go in the top left block? 7 9 3 4 7 5 2 1 3 • Did you get it right? 3 7 3 4**Step #17**4 2 8 9 3 • There is only one number to go in the top left block • What number has not been used? 7 9 3 4 7 5 2 1 3 • Did you get it right? 3 7 3 4**Step #18**4 2 8 9 6 3 • There is only one number to go in the top row • What number has not been used? • Did you get it right? 7 9 3 4 7 5 2 1 3 3 7 3 4**Step #19**4 2 8 9 6 3 • There is only one number to go in the second row • What number has not been used? • Did you get it right? 5 7 9 3 4 7 5 2 1 3 3 7 3 4**Step #20**4 2 8 9 6 3 • There are two numbers that need to go in the top right block • What numbers have not been used? 7 9 3 4 5 7 5 2 1 3 3 7 3 4**Step #20**4 2 8 9 6 3 • The two numbers are 9 and 1 • The 9 can only go in one cell because there is a 9 in one of the columns 7 9 3 4 5 7 5 2 9 1 1 3 • Did you get it right? 3 7 • The number 1 will go in the last cell. 3 4**Step #21**4 2 8 9 6 3 • There are two numbers that need to go in this row • What two numbers have not been used? 7 9 3 4 5 7 5 2 9 1 1 3 3 7 3 4**Step #21**• The 2 cannot go in the second column twice, so it must go in the 5th column 4 2 8 9 6 3 7 9 3 4 5 7 5 2 9 1 1 8 2 3 • The 8 cannot go in the 5th column, so it must go in the 2nd column 3 7 3 4**Step #22**4 2 8 9 6 3 7 9 3 4 5 • Fill in the missing number in this column 7 5 2 9 1 1 8 2 3 6 3 7 3 4