LeetCode-36-有效的数独
36. 有效的数独
难度中等516收藏分享切换为英文接收动态反馈
请你判断一个 9x9 的数独是否有效。只需要 根据以下规则 ，验证已经填入的数字是否有效即可。
- 数字
1-9在每一行只能出现一次。 - 数字
1-9在每一列只能出现一次。 - 数字
1-9在每一个以粗实线分隔的3x3宫内只能出现一次。（请参考示例图）
数独部分空格内已填入了数字，空白格用 '.' 表示。
注意：
- 一个有效的数独（部分已被填充）不一定是可解的。
- 只需要根据以上规则，验证已经填入的数字是否有效即可。
示例 1：
img
输入：board =
[["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"]]
输出：true
示例 2：
输入：board =
[["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"]]
输出：false
解释：除了第一行的第一个数字从 5 改为 8 以外，空格内其他数字均与 示例1 相同。 但由于位于左上角的 3x3 宫内有两个 8 存在, 因此这个数独是无效的。
提示：
board.length == 9board[i].length == 9-
board[i][j]是一位数字或者'.'
准备三个有效验证的数组
boolean[][] row = new boolean[9][10];
boolean[][] col = new boolean[9][10];
boolean[][] bucket = new boolean[9][10];
row[2][7] 表示 第2行 7数字已经出现了
col[2][7] 表示 第2列 7数字已经出现了
bucket[2][7] 表示 第2个9*9的格子 7数字已经出现了
class Solution {
public static boolean isValidSudoku(char[][] board) {
boolean[][] row = new boolean[9][10];
boolean[][] col = new boolean[9][10];
boolean[][] bucket = new boolean[9][10];
for (int i = 0; i < 9; i++) {
for (int j = 0; j < 9; j++) {
int bid = 3 * (i / 3) + (j / 3);
if (board[i][j] != '.') {
int num = board[i][j] - '0';
if (row[i][num] || col[j][num] || bucket[bid][num]) {
return false;
}
row[i][num] = true;
col[j][num] = true;
bucket[bid][num] = true;
}
}
}
return true;
}
}
image
LeetCode-37-解数独
37. 解数独
难度困难830收藏分享切换为英文接收动态反馈
编写一个程序，通过填充空格来解决数独问题。
数独的解法需 遵循如下规则：
- 数字
1-9在每一行只能出现一次。 - 数字
1-9在每一列只能出现一次。 - 数字
1-9在每一个以粗实线分隔的3x3宫内只能出现一次。（请参考示例图）
数独部分空格内已填入了数字，空白格用 '.' 表示。
示例：
img
输入：board = [["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"]]
输出：[["5","3","4","6","7","8","9","1","2"],["6","7","2","1","9","5","3","4","8"],["1","9","8","3","4","2","5","6","7"],["8","5","9","7","6","1","4","2","3"],["4","2","6","8","5","3","7","9","1"],["7","1","3","9","2","4","8","5","6"],["9","6","1","5","3","7","2","8","4"],["2","8","7","4","1","9","6","3","5"],["3","4","5","2","8","6","1","7","9"]]
解释：输入的数独如上图所示，唯一有效的解决方案如下所示：
250px-sudoku-by-l2g-20050714_solutionsvg.png
提示：
board.length == 9board[i].length == 9-
board[i][j]是一位数字或者'.' - 题目数据 保证 输入数独仅有一个解
使用第36题的有效性过滤条件来尝试填入的数字
for (int num = 1; num <= 9; num++) 每个格子使用1~9填入数字尝试
尝试前判断一下填入数组的有效性if ((!row[i][num]) && (!col[j][num]) && (!bucket[bid][num]))
image
class Solution {
public static void solveSudoku(char[][] board) {
boolean[][] row = new boolean[9][10];
boolean[][] col = new boolean[9][10];
boolean[][] bucket = new boolean[9][10];
initMaps(board, row, col, bucket);
process(board, 0, 0, row, col, bucket);
}
public static void initMaps(char[][] board, boolean[][] row, boolean[][] col, boolean[][] bucket) {
for (int i = 0; i < 9; i++) {
for (int j = 0; j < 9; j++) {
int bid = 3 * (i / 3) + (j / 3);
if (board[i][j] != '.') {
int num = board[i][j] - '0';
row[i][num] = true;
col[j][num] = true;
bucket[bid][num] = true;
}
}
}
}
public static boolean process(char[][] board, int i, int j, boolean[][] row, boolean[][] col, boolean[][] bucket) {
if (i == 9) {
return true;
}
int nexti = j != 8 ? i : i + 1;
int nextj = j != 8 ? j + 1 : 0;
if (board[i][j] != '.') {
return process(board, nexti, nextj, row, col, bucket);
} else {
int bid = 3 * (i / 3) + (j / 3);
for (int num = 1; num <= 9; num++) {
if ((!row[i][num]) && (!col[j][num]) && (!bucket[bid][num])) {
row[i][num] = true;
col[j][num] = true;
bucket[bid][num] = true;
board[i][j] = (char) (num + '0');
if (process(board, nexti, nextj, row, col, bucket)) {
return true;
}
row[i][num] = false;
col[j][num] = false;
bucket[bid][num] = false;
board[i][j] = '.';
}
}
return false;
}
}
}
image
