蓝桥杯之穿越雷区
广度优先算法：
import java.util.LinkedList;
import java.util.Queue;
import java.util.Scanner;
public class LanQiao29 {
static boolean[][] isVisted;
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
char[][] board = new char[n][n];
isVisted = new boolean[n][n];
int row = 0;
int column = 0;
for (int i = 0; i < n; i++) {
for (int j = 0; j < n; j++) {
board[i][j] = sc.next().charAt(0);
if (board[i][j] == 'A') {
//记录'A'所在的行和列
row = i;
column = j;
}
}
}
bfs(board, row, column, n);
/*
int[][] next = {
{-1, 0}, {0, -1}, {1, 0}, {0, 1}};//next数组用来表示方向，即往哪里移动
bfs1(board, next, row, column, n);
*/
}
public static void bfs(char[][] board, int row, int column, int n) {
Queue<int[]> queue = new LinkedList<>();
queue.add(new int[]{
row, column, 0});//行、列、步数
int temp = 0;
while (!queue.isEmpty()) {
int[] arr = queue.poll();
int i = arr[0];
int j = arr[1];
int curStep = arr[2];
isVisted[i][j] = true;
if ((i - 1) >= 0 && !isVisted[i - 1][j] && board[i][j] != board[i - 1][j]) {
queue.add(new int[]{
i - 1, j, curStep + 1});
}
if ((j - 1) >= 0 && !isVisted[i][j - 1] && board[i][j] != board[i][j - 1]) {
queue.add(new int[]{
i, j - 1, curStep + 1});
}
if ((i + 1) < n && !isVisted[i + 1][j] && board[i][j] != board[i + 1][j]) {
queue.add(new int[]{
i + 1, j, curStep + 1});
}
if ((j + 1) < n && !isVisted[i][j + 1] && board[i][j] != board[i][j + 1]) {
queue.add(new int[]{
i, j + 1, curStep + 1});
}
if (board[i][j] == 'B') {
System.out.println(curStep);
return;
}
}
System.out.println(-1);
}
//other version
public static void bfs1(char[][] board, int[][] next, int row, int column, int n) {
Queue<int[]> queue = new LinkedList<>();
queue.add(new int[]{
row, column, 0});//行、列、步数
while (!queue.isEmpty()) {
int[] arr = queue.poll();
int i = arr[0];
int j = arr[1];
int curStep = arr[2];
isVisted[i][j] = true;
for (int k = 0; k < 4; k++) {
int nextX = i + next[k][0];
int nextY = j + next[k][1];
if (nextX < 0 || nextX >= n || nextY < 0 || nextY >= n) {
continue;
}
if (!isVisted[nextX][nextY] && board[i][j] != board[nextX][nextY]) {
queue.add(new int[]{
nextX, nextY, curStep + 1});
}
}
if (board[i][j] == 'B') {
System.out.println(curStep);
return;
}
}
System.out.println(-1);
}
}
深度优先算法：
import java.util.Arrays;
import java.util.LinkedList;
import java.util.Queue;
import java.util.Scanner;
public class LanQiao29 {
static int res = Integer.MAX_VALUE;
static int step = 0;
static boolean[][] isVisted;
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
char[][] board = new char[n][n];
isVisted = new boolean[n][n];
int row = 0;
int column = 0;
for (int i = 0; i < n; i++) {
for (int j = 0; j < n; j++) {
board[i][j] = sc.next().charAt(0);
if (board[i][j] == 'A') {
//记录'A'所在的行和列
row = i;
column = j;
}
}
}
dfs(board, row, column, n);
if (res == Integer.MAX_VALUE) {
System.out.println(-1);
} else {
System.out.println(res);
}
/*
int[][] next = {
{-1, 0}, {0, -1}, {1, 0}, {0, 1}};//next数组用来表示方向，即往哪里移动
dfs1(board, next, row, column, n);
System.out.println(res);
*/
}
public static void dfs(char[][] board, int i, int j, int n) {
if (board[i][j] == 'B') {
res = Integer.min(res, step);
return;
}
isVisted[i][j] = true;
step++;
if ((i - 1) >= 0 && !isVisted[i - 1][j] && board[i][j] != board[i - 1][j]) {
dfs(board, i - 1, j, n);
}
if ((j - 1) >= 0 && !isVisted[i][j - 1] && board[i][j] != board[i][j - 1]) {
dfs(board, i, j - 1, n);
}
if ((i + 1) < n && !isVisted[i + 1][j] && board[i][j] != board[i + 1][j]) {
dfs(board, i + 1, j, n);
}
if ((j + 1) < n && !isVisted[i][j + 1] && board[i][j] != board[i][j + 1]) {
dfs(board, i, j + 1, n);
}
isVisted[i][j] = false;
step--;
}
//other version
public static void dfs1(char[][] board, int[][] next, int i, int j, int n) {
isVisted[i][j] = true;
if (board[i][j] == 'B') {
res = Integer.min(res, step);
return;
}
for (int k = 0; k < 4; k++) {
int nextX = i + next[k][0];
int nextY = j + next[k][1];
if (nextX < 0 || nextX >= n || nextY < 0 || nextY >= n) {
continue;
}
if (!isVisted[nextX][nextY] && board[i][j] != board[nextX][nextY]) {
//isVisted[nextX][nextY] = true;//可以有可以没有
step++;
dfs1(board, next, nextX, nextY, n);
isVisted[nextX][nextY] = false;
step--;
}
}
}
}