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1 | 1 | classSolution { |
2 | 2 |
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3 | 3 | publicbooleanisValidSudoku(char[][]board) { |
4 | | -introws =board.length; |
5 | | -intcols =board[0].length; |
| 4 | +//neetcode solution, slightly modified |
6 | 5 |
|
| 6 | +//a set of the characters that we have already come across (excluding '.' which denotes an empty space) |
7 | 7 | Set<Character>rowSet =null; |
8 | 8 | Set<Character>colSet =null; |
9 | 9 |
|
10 | | -//check for rows |
11 | | -for (inti =0;i <rows;i++) { |
12 | | -rowSet =newHashSet<>(); |
13 | | -for (intj =0;j <cols;j++) { |
14 | | -if (board[i][j] =='.') { |
15 | | -continue; |
16 | | - } |
17 | | -if (rowSet.contains(board[i][j])) { |
18 | | -returnfalse; |
19 | | - } |
20 | | -rowSet.add(board[i][j]); |
21 | | - } |
22 | | - } |
23 | 10 |
|
24 | | -//check for cols |
25 | | -for (inti =0;i <cols;i++) { |
| 11 | +for (inti =0;i <9;i++) { |
| 12 | +//reinitialize the sets so we don't carry over found characters from the previous run |
| 13 | +rowSet =newHashSet<>(); |
26 | 14 | colSet =newHashSet<>(); |
27 | | -for (intj =0;j <rows;j++) { |
28 | | -if (board[j][i] =='.') { |
29 | | -continue; |
| 15 | +for (intj =0;j <9;j++) { |
| 16 | +charr =board[i][j]; |
| 17 | +charc =board[j][i]; |
| 18 | +if (r !='.'){ |
| 19 | +if (rowSet.contains(r)){ |
| 20 | +returnfalse; |
| 21 | + }else { |
| 22 | +rowSet.add(r); |
| 23 | + } |
30 | 24 | } |
31 | | -if (colSet.contains(board[j][i])) { |
32 | | -returnfalse; |
| 25 | +if (c !='.'){ |
| 26 | +if (colSet.contains(c)){ |
| 27 | +returnfalse; |
| 28 | + }else { |
| 29 | +colSet.add(c); |
| 30 | + } |
33 | 31 | } |
34 | | - |
35 | | -colSet.add(board[j][i]); |
36 | 32 | } |
37 | 33 | } |
38 | 34 |
|
39 | 35 | //block |
40 | | -for (inti =0;i <rows;i =i +3) { |
41 | | -for (intj =0;j <cols;j =j +3) { |
| 36 | +//loop controls advance by 3 each time to jump through the boxes |
| 37 | +for (inti =0;i <9;i =i +3) { |
| 38 | +for (intj =0;j <9;j =j +3) { |
| 39 | +//checkBlock will return true if valid |
42 | 40 | if (!checkBlock(i,j,board)) { |
43 | 41 | returnfalse; |
44 | 42 | } |
45 | 43 | } |
46 | 44 | } |
47 | | - |
| 45 | +//passed all tests, therefore valid board |
48 | 46 | returntrue; |
49 | 47 | } |
50 | 48 |
|
51 | 49 | publicbooleancheckBlock(intidxI,intidxJ,char[][]board) { |
52 | 50 | Set<Character>blockSet =newHashSet<>(); |
| 51 | +//if idxI = 3 and indJ = 0 |
| 52 | +//rows = 6 and cols = 3 |
53 | 53 | introws =idxI +3; |
54 | 54 | intcols =idxJ +3; |
| 55 | +//and because i initializes to idxI but only goes to rows, we loop 3 times (once for each row) |
55 | 56 | for (inti =idxI;i <rows;i++) { |
| 57 | +//same for columns |
56 | 58 | for (intj =idxJ;j <cols;j++) { |
57 | 59 | if (board[i][j] =='.') { |
58 | 60 | continue; |
59 | 61 | } |
60 | | - |
| 62 | +
|
61 | 63 | if (blockSet.contains(board[i][j])) { |
62 | 64 | returnfalse; |
63 | 65 | } |
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