diff --git a/problems/0130.被围绕的区域.md b/problems/0130.被围绕的区域.md index c2aa5696..7afa71b4 100644 --- a/problems/0130.被围绕的区域.md +++ b/problems/0130.被围绕的区域.md @@ -84,7 +84,221 @@ public: ## 其他语言版本 +### Java + +```Java +// 广度优先遍历 +// 使用 visited 数组进行标记 +class Solution { + private static final int[][] position = {{-1, 0}, {0, 1}, {1, 0}, {0, -1}}; // 四个方向 + + public void solve(char[][] board) { + // rowSize:行的长度,colSize:列的长度 + int rowSize = board.length, colSize = board[0].length; + boolean[][] visited = new boolean[rowSize][colSize]; + Queue queue = new ArrayDeque<>(); + // 从左侧边,和右侧边遍历 + for (int row = 0; row < rowSize; row++) { + if (board[row][0] == 'O') { + visited[row][0] = true; + queue.add(new int[]{row, 0}); + } + if (board[row][colSize - 1] == 'O') { + visited[row][colSize - 1] = true; + queue.add(new int[]{row, colSize - 1}); + } + } + // 从上边和下边遍历,在对左侧边和右侧边遍历时我们已经遍历了矩阵的四个角 + // 所以在遍历上边和下边时可以不用遍历四个角 + for (int col = 1; col < colSize - 1; col++) { + if (board[0][col] == 'O') { + visited[0][col] = true; + queue.add(new int[]{0, col}); + } + if (board[rowSize - 1][col] == 'O') { + visited[rowSize - 1][col] = true; + queue.add(new int[]{rowSize - 1, col}); + } + } + // 广度优先遍历,把没有被 'X' 包围的 'O' 进行标记 + while (!queue.isEmpty()) { + int[] current = queue.poll(); + for (int[] pos: position) { + int row = current[0] + pos[0], col = current[1] + pos[1]; + // 如果范围越界、位置已被访问过、该位置的值不是 'O',就直接跳过 + if (row < 0 || row >= rowSize || col < 0 || col >= colSize) continue; + if (visited[row][col] || board[row][col] != 'O') continue; + visited[row][col] = true; + queue.add(new int[]{row, col}); + } + } + // 遍历数组,把没有被标记的 'O' 修改成 'X' + for (int row = 0; row < rowSize; row++) { + for (int col = 0; col < colSize; col++) { + if (board[row][col] == 'O' && !visited[row][col]) board[row][col] = 'X'; + } + } + } +} +``` +```Java +// 广度优先遍历 +// 直接修改 board 的值为其他特殊值 +class Solution { + private static final int[][] position = {{-1, 0}, {0, 1}, {1, 0}, {0, -1}}; // 四个方向 + + public void solve(char[][] board) { + // rowSize:行的长度,colSize:列的长度 + int rowSize = board.length, colSize = board[0].length; + Queue queue = new ArrayDeque<>(); + // 从左侧边,和右侧边遍历 + for (int row = 0; row < rowSize; row++) { + if (board[row][0] == 'O') + queue.add(new int[]{row, 0}); + if (board[row][colSize - 1] == 'O') + queue.add(new int[]{row, colSize - 1}); + } + // 从上边和下边遍历,在对左侧边和右侧边遍历时我们已经遍历了矩阵的四个角 + // 所以在遍历上边和下边时可以不用遍历四个角 + for (int col = 1; col < colSize - 1; col++) { + if (board[0][col] == 'O') + queue.add(new int[]{0, col}); + if (board[rowSize - 1][col] == 'O') + queue.add(new int[]{rowSize - 1, col}); + } + // 广度优先遍历,把没有被 'X' 包围的 'O' 修改成特殊值 + while (!queue.isEmpty()) { + int[] current = queue.poll(); + board[current[0]][current[1]] = 'A'; + for (int[] pos: position) { + int row = current[0] + pos[0], col = current[1] + pos[1]; + // 如果范围越界、该位置的值不是 'O',就直接跳过 + if (row < 0 || row >= rowSize || col < 0 || col >= colSize) continue; + if (board[row][col] != 'O') continue; + queue.add(new int[]{row, col}); + } + } + // 遍历数组,把 'O' 修改成 'X',特殊值修改成 'O' + for (int row = 0; row < rowSize; row++) { + for (int col = 0; col < colSize; col++) { + if (board[row][col] == 'A') board[row][col] = 'O'; + else if (board[row][col] == 'O') board[row][col] = 'X'; + } + } + } +} +``` +```Java +// 深度优先遍历 +// 使用 visited 数组进行标记 +class Solution { + private static final int[][] position = {{-1, 0}, {0, 1}, {1, 0}, {0, -1}}; // 四个方向 + + public void dfs(char[][] board, int row, int col, boolean[][] visited) { + for (int[] pos: position) { + int nextRow = row + pos[0], nextCol = col + pos[1]; + // 位置越界 + if (nextRow < 0 || nextRow >= board.length || nextCol < 0 || nextCol >= board[0].length) + continue; + // 位置已被访问过、新位置值不是 'O' + if (visited[nextRow][nextCol] || board[nextRow][nextCol] != 'O') continue; + visited[nextRow][nextCol] = true; + dfs(board, nextRow, nextCol, visited); + } + } + + public void solve(char[][] board) { + int rowSize = board.length, colSize = board[0].length; + boolean[][] visited = new boolean[rowSize][colSize]; + // 从左侧遍、右侧遍遍历 + for (int row = 0; row < rowSize; row++) { + if (board[row][0] == 'O' && !visited[row][0]) { + visited[row][0] = true; + dfs(board, row, 0, visited); + } + if (board[row][colSize - 1] == 'O' && !visited[row][colSize - 1]) { + visited[row][colSize - 1] = true; + dfs(board, row, colSize - 1, visited); + } + } + // 从上边和下边遍历,在对左侧边和右侧边遍历时我们已经遍历了矩阵的四个角 + // 所以在遍历上边和下边时可以不用遍历四个角 + for (int col = 1; col < colSize - 1; col++) { + if (board[0][col] == 'O' && !visited[0][col]) { + visited[0][col] = true; + dfs(board, 0, col, visited); + } + if (board[rowSize - 1][col] == 'O' && !visited[rowSize - 1][col]) { + visited[rowSize - 1][col] = true; + dfs(board, rowSize - 1, col, visited); + } + } + // 遍历数组,把没有被标记的 'O' 修改成 'X' + for (int row = 0; row < rowSize; row++) { + for (int col = 0; col < colSize; col++) { + if (board[row][col] == 'O' && !visited[row][col]) board[row][col] = 'X'; + } + } + } +} +``` +```Java +// 深度优先遍历 +// // 直接修改 board 的值为其他特殊值 +class Solution { + private static final int[][] position = {{-1, 0}, {0, 1}, {1, 0}, {0, -1}}; // 四个方向 + + public void dfs(char[][] board, int row, int col) { + for (int[] pos: position) { + int nextRow = row + pos[0], nextCol = col + pos[1]; + // 位置越界 + if (nextRow < 0 || nextRow >= board.length || nextCol < 0 || nextCol >= board[0].length) + continue; + // 新位置值不是 'O' + if (board[nextRow][nextCol] != 'O') continue; + board[nextRow][nextCol] = 'A'; // 修改为特殊值 + dfs(board, nextRow, nextCol); + } + } + + public void solve(char[][] board) { + int rowSize = board.length, colSize = board[0].length; + // 从左侧遍、右侧遍遍历 + for (int row = 0; row < rowSize; row++) { + if (board[row][0] == 'O') { + board[row][0] = 'A'; + dfs(board, row, 0); + } + if (board[row][colSize - 1] == 'O') { + board[row][colSize - 1] = 'A'; + dfs(board, row, colSize - 1); + } + } + // 从上边和下边遍历,在对左侧边和右侧边遍历时我们已经遍历了矩阵的四个角 + // 所以在遍历上边和下边时可以不用遍历四个角 + for (int col = 1; col < colSize - 1; col++) { + if (board[0][col] == 'O') { + board[0][col] = 'A'; + dfs(board, 0, col); + } + if (board[rowSize - 1][col] == 'O') { + board[rowSize - 1][col] = 'A'; + dfs(board, rowSize - 1, col); + } + } + // 遍历数组,把 'O' 修改成 'X',特殊值修改成 'O' + for (int row = 0; row < rowSize; row++) { + for (int col = 0; col < colSize; col++) { + if (board[row][col] == 'O') board[row][col] = 'X'; + else if (board[row][col] == 'A') board[row][col] = 'O'; + } + } + } +} +``` +

+ diff --git a/problems/0797.所有可能的路径.md b/problems/0797.所有可能的路径.md index eb3f7fb4..89643e04 100644 --- a/problems/0797.所有可能的路径.md +++ b/problems/0797.所有可能的路径.md @@ -161,6 +161,35 @@ public: ## Java +```Java +// 深度优先遍历 +class Solution { + List> ans; // 用来存放满足条件的路径 + List cnt; // 用来保存 dfs 过程中的节点值 + + public void dfs(int[][] graph, int node) { + if (node == graph.length - 1) { // 如果当前节点是 n - 1,那么就保存这条路径 + ans.add(new ArrayList<>(cnt)); + return; + } + for (int index = 0; index < graph[node].length; index++) { + int nextNode = graph[node][index]; + cnt.add(nextNode); + dfs(graph, nextNode); + cnt.remove(cnt.size() - 1); // 回溯 + } + } + + public List> allPathsSourceTarget(int[][] graph) { + ans = new ArrayList<>(); + cnt = new ArrayList<>(); + cnt.add(0); // 注意,0 号节点要加入 cnt 数组中 + dfs(graph, 0); + return ans; + } +} +``` + ## Python ```python class Solution: @@ -192,3 +221,4 @@ class Solution: +