# Why would this input result in an invalid Sudoku?

• For input ["....5..1.",".4.3.....",".....3..1","8......2.","..2.7....",".15......",".....2...",".2.9.....","..4......"] my program returns true but the expected output is supposed to be false as reported by OJ? Can someone help me see why it is invalid?

I gave the same input to my Sudoku solver to ensure there is a solution and it can be solved as below - which makes it more confusing on why it is invalid:

. . . . 5 . . 1 .

. 4 . 3 . . . . .

. . . . . 3 . . 1

8 . . . . . . 2 .

. . 2 . 7 . . . .

. 1 5 . . . . . .

. . . . . 2 . . .

. 2 . 9 . . . . .

. . 4 . . . . . .

Solved as:

2 3 7 4 5 6 8 1 9

1 4 8 3 9 7 2 5 6

5 6 9 2 8 3 4 7 1

8 7 6 1 3 4 9 2 5

3 9 2 5 7 8 1 6 4

4 1 5 6 2 9 3 8 7

6 5 1 8 4 2 7 9 3

7 2 3 9 1 5 6 4 8

9 8 4 7 6 1 5 3 2

• 2 3 7 4 5 6 8 [1] 9

1 4 8 3 9 7 2 5 6

5 6 9 2 8 3 4 7 [1]

8 7 6 1 3 4 9 2 5

3 9 2 5 7 8 1 6 4

4 1 5 6 2 9 3 8 7

6 5 1 8 4 2 7 9 3

7 2 3 9 1 5 6 4 8

9 8 4 7 6 1 5 3 2

Those [1] in the same block. You looks misundertand the rules of sudoku.

• It is not valid. Look at the bold part. It contains two '1'.

2 3 7 4 5 6 8 1 9

1 4 8 3 9 7 2 5 6

5 6 9 2 8 3 4 7 1

8 7 6 1 3 4 9 2 5

3 9 2 5 7 8 1 6 4

4 1 5 6 2 9 3 8 7

6 5 1 8 4 2 7 9 3

7 2 3 9 1 5 6 4 8

9 8 4 7 6 1 5 3 2

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