前言
持续更新了
正文
问题来源
本问题来自leetcode上的37题。
问题描述
编写一个程序，通过已填充的空格来解决数独问题。
一个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。
示例 1:
输入: nums = [["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: [1,2]
示例 2:
[["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"]]
分析：
func solveSudoku(board [][]byte) {
left := make([]int, 0)
for i := 0; i < 9; i++ {
for j := 0; j < 9; j++ {
if board[i][j] == '.' {
left = append(left, i*10+j)
}
}
}
dfs(board, 0, left)
}
func dfs(board [][]byte, count int, left []int) bool {
if count == len(left) {
return true
}
location := left[count]
i, j := location/10, location%10
var k byte
for k = '1'; k <= '9'; k++ {
if canfill(board, i, j, k) {
board[i][j] = k
if dfs(board, count+1, left) {
return true
}
board[i][j] = '.'
}
}
return false
}
func canfill(board [][]byte, i, j int, k byte) bool {
for x := 0; x < 9; x++ {
if board[i][x] == k {
return false
}
}
for x := 0; x < 9; x++ {
if board[x][j] == k {
return false
}
}
si, sj := i/3, j/3
for x := 0; x < 3; x++ {
for y := 0; y < 3; y++ {
if board[si*3+x][sj*3+y] == k {
return false
}
}
}
return true
}
总结：
勤思考。
结语
不管怎么样好好加油。
