2021-10-14:被围绕的区域。给你一个 m x n 的矩阵 board ,由若干字符 ‘X‘ 和 ‘O‘ ,找到所有被 ‘X‘ 围绕的区域,并将这些区域里所有的 ‘O‘ 用 ‘X‘ 填充。力扣1
2021-10-14:被围绕的区域。给你一个 m x n 的矩阵 board ,由若干字符 ‘X’ 和 ‘O’ ,找到所有被 ‘X’ 围绕的区域,并将这些区域里所有的 ‘O’ 用 ‘X’ 填充。力扣130。
福大大 答案2021-10-14:
从四周边界开始感染,没感染到的区域,变成’X’。
时间复杂度:O(MN)。
空间复杂度:未知。
代码用golang编写。代码如下:
package main
import "fmt"
func main() {
if true {
board := [][]byte{{'X', 'X', 'X', 'X'}, {'X', 'O', 'O', 'X'}, {'X', 'X', 'O', 'X'}, {'X', 'O', 'X', 'X'}}
solve1(board)
for i := 0; i < len(board); i++ {
for j := 0; j < len(board[i]); j++ {
fmt.Printf("%c ", board[i][j])
}
fmt.Println("")
}
}
fmt.Println("---------")
if true {
board := [][]byte{{'X', 'X', 'X', 'X'}, {'X', 'O', 'O', 'X'}, {'X', 'X', 'O', 'X'}, {'X', 'O', 'X', 'X'}}
solve2(board)
for i := 0; i < len(board); i++ {
for j := 0; j < len(board[i]); j++ {
fmt.Printf("%c ", board[i][j])
}
fmt.Println("")
}
}
}
// // m -> 二维数组, 不是0就是1
// //
// public static void infect(int[][] m, int i, int j) {
// if (i < 0 || i == m.length || j < 0 || j == m[0].length || m[i][j] != 1) {
// return;
// }
// // m[i][j] == 1
// m[i][j] = 2;
// infect(m, i - 1, j);
// infect(m, i + 1, j);
// infect(m, i, j - 1);
// infect(m, i, j + 1);
// }
func solve1(board [][]byte) {
ans := make([]bool, 1)
for i := 0; i < len(board); i++ {
for j := 0; j < len(board[0]); j++ {
if board[i][j] == 'O' {
ans[0] = true
can(board, i, j, ans)
if ans[0] {
board[i][j] = 'T'
} else {
board[i][j] = 'F'
}
}
}
}
for i := 0; i < len(board); i++ {
for j := 0; j < len(board[0]); j++ {
can := board[i][j]
if can == 'T' || can == 'F' {
board[i][j] = '.'
change(board, i, j, can)
}
}
}
}
func can(board [][]byte, i int, j int, ans []bool) {
if i < 0 || i == len(board) || j < 0 || j == len(board[0]) {
ans[0] = false
return
}
if board[i][j] == 'O' {
board[i][j] = '.'
can(board, i-1, j, ans)
can(board, i+1, j, ans)
can(board, i, j-1, ans)
can(board, i, j+1, ans)
}
}
func change(board [][]byte, i int, j int, can byte) {
if i < 0 || i == len(board) || j < 0 || j == len(board[0]) {
return
}
if board[i][j] == '.' {
if can == 'T' {
board[i][j] = 'X'
} else {
board[i][j] = '0'
}
change(board, i-1, j, can)
change(board, i+1, j, can)
change(board, i, j-1, can)
change(board, i, j+1, can)
}
}
// 从边界开始感染的方法,比第一种方法更好
func solve2(board [][]byte) {
if len(board) == 0 || len(board[0]) == 0 {
return
}
N := len(board)
M := len(board[0])
for j := 0; j < M; j++ {
if board[0][j] == 'O' {
free(board, 0, j)
}
if board[N-1][j] == 'O' {
free(board, N-1, j)
}
}
for i := 1; i < N-1; i++ {
if board[i][0] == 'O' {
free(board, i, 0)
}
if board[i][M-1] == 'O' {
free(board, i, M-1)
}
}
for i := 0; i < N; i++ {
for j := 0; j < M; j++ {
if board[i][j] == 'O' {
board[i][j] = 'X'
}
if board[i][j] == 'F' {
board[i][j] = 'O'
}
}
}
}
func free(board [][]byte, i int, j int) {
if i < 0 || i == len(board) || j < 0 || j == len(board[0]) || board[i][j] != 'O' {
return
}
board[i][j] = 'F'
free(board, i+1, j)
free(board, i-1, j)
free(board, i, j+1)
free(board, i, j-1)
}
执行结果如下:
公众号:福大大架构师每日一题