题目来源：https://leetcode.com/problems/valid-sudoku/
问题描述
36. Valid Sudoku
Medium
Determine if a 9x9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules:
- Each row must contain the digits 1-9 without repetition.
- Each column must contain the digits 1-9 without repetition.
- Each of the 9 3x3 sub-boxes of the grid must contain the digits 1-9 without repetition.
The Sudoku board could be partially filled, where empty cells are filled with the character '.'.
Example 1:
Input:
[
["5","3",".",".","7",".",".",".","."],
["6",".",".","1","9","5",".",".","."],
[".","9","8",".",".",".",".","6","."],
["8",".",".",".","6",".",".",".","3"],
["4",".",".","8",".","3",".",".","1"],
["7",".",".",".","2",".",".",".","6"],
[".","6",".",".",".",".","2","8","."],
[".",".",".","4","1","9",".",".","5"],
[".",".",".",".","8",".",".","7","9"]
]
Output: true
Example 2:
Input:
[
["8","3",".",".","7",".",".",".","."],
["6",".",".","1","9","5",".",".","."],
[".","9","8",".",".",".",".","6","."],
["8",".",".",".","6",".",".",".","3"],
["4",".",".","8",".","3",".",".","1"],
["7",".",".",".","2",".",".",".","6"],
[".","6",".",".",".",".","2","8","."],
[".",".",".","4","1","9",".",".","5"],
[".",".",".",".","8",".",".","7","9"]
]
Output: false
Explanation: Same as Example 1, except with the 5 in the top left corner being
modified to 8. Since there are two 8's in the top left 3x3 sub-box, it is invalid.
Note:
- A Sudoku board (partially filled) could be valid but is not necessarily solvable.
- Only the filled cells need to be validated according to the mentioned rules.
- The given board contain only digits 1-9 and the character '.'.
- The given board size is always 9x9.
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题意
给定一个升序序列nums和一个数target，如果target在nums中则返回target的位置，否则返回target应该插入的位置。
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思路
暴力遍历判断即可。
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代码
class Solution {
public static final int[] BLOCK_X = {0, 0, 0, 3, 3, 3, 6, 6, 6};
public static final int[] BLOCK_Y = {0, 3, 6, 0, 3, 6, 0, 3, 6};
public boolean[] digits = new boolean[9];
public boolean isValidSudoku(char[][] board) {
int i = 0, j = 0;
char ch = 0;
int val = -1;
// check rows
for (i=0; i<9; i++)
{
Arrays.fill(digits, false);
for (j=0; j<9; j++)
{
ch = board[i][j];
if (ch == '.')
{
continue;
}
else
{
val = Character.getNumericValue(ch) - 1;
if (digits[val])
{
return false;
}
else
{
digits[val] = true;
}
}
}
}
// check columns
for (i=0; i<9; i++)
{
Arrays.fill(digits, false);
for (j=0; j<9; j++)
{
ch = board[j][i];
if (ch == '.')
{
continue;
}
else
{
val = Character.getNumericValue(ch) - 1;
if (digits[val])
{
return false;
}
else
{
digits[val] = true;
}
}
}
}
// check 3x3 blocks
for (int block = 0; block < 9; block++)
{
Arrays.fill(digits, false);
for (i=0; i<3; i++)
{
for (j=0; j<3; j++)
{
ch = board[BLOCK_X[block]+i][BLOCK_Y[block]+j];
if (ch == '.')
{
continue;
}
else
{
val = Character.getNumericValue(ch) - 1;
if (digits[val])
{
return false;
}
else
{
digits[val] = true;
}
}
}
}
}
return true;
}
}