LeetCode 1034 边界着色

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LeetCode 1034 边界着色
给你一个大小为 m x n 的整数矩阵 grid ，表示一个网格。另给你三个整数 row、col 和 color 。网格中的每个值表示该位置处的网格块的颜色。

当两个网格块的颜色相同，而且在四个方向中任意一个方向上相邻时，它们属于同一 连通分量 。

连通分量的边界 是指连通分量中的所有与不在分量中的网格块相邻（四个方向上）的所有网格块，或者在网格的边界上（第一行/列或最后一行/列）的所有网格块。

请你使用指定颜色 color 为所有包含网格块 grid[row][col] 的 连通分量的边界 进行着色，并返回最终的网格 grid 。

示例 1：
```
输入：grid = [[1,1],[1,2]], row = 0, col = 0, color = 3
输出：[[3,3],[3,2]]
```
示例 2：
```
输入：grid = [[1,2,2],[2,3,2]], row = 0, col = 1, color = 3
输出：[[1,3,3],[2,3,3]]
```
示例 3：
```
输入：grid = [[1,1,1],[1,1,1],[1,1,1]], row = 1, col = 1, color = 2
输出：[[2,2,2],[2,1,2],[2,2,2]]
```
提示：
- m == grid.length
- n == grid[i].length
- 1 <= m, n <= 50
- 1 <= grid[i][j], color <= 1000
- 0 <= row < m
- 0 <= col < n
Related Topics
深度优先搜索
广度优先搜索
数组
矩阵

深度优先

/**
 * DFS
 *
 * @param grid
 * @param row
 * @param col
 * @param color
 * @return
 */
public static int[][] colorBorder(int[][] grid, int row, int col, int color) {
    if (grid == null || grid.length == 0 || grid[0].length == 0) {
        return new int[][]{};
    }

    // 判断是否为边界
    int rows = grid.length;
    int cols = grid[0].length;

    // 表示该位置是否为边界
    boolean[][] colorFlag = new boolean[rows][cols];
    // 表示该位置是否已遍历
    boolean[][] flag = new boolean[rows][cols];
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < cols; j++) {
            colorFlag[i][j] = false;
            flag[i][j] = false;
        }
    }

    int target = grid[row][col];
    dfs(grid, target, row, col, colorFlag, flag);
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < cols; j++) {
            if (colorFlag[i][j] == true) {
                grid[i][j] = color;
            }
        }
    }
    return grid;
}

private static void dfs(int[][] grid, int target,
                        int i, int j,
                        boolean[][] colorFlag,
                        boolean[][] flag) {

    if (i < 0 || i >= grid.length
            || j < 0 || j >= grid[0].length
            || grid[i][j] != target || flag[i][j]) {
        return;
    }
    flag[i][j] = true;
    colorFlag[i][j] = true;
    if (i > 0) {
        dfs(grid, target, i - 1, j, colorFlag, flag);
    }
    if (i < grid.length - 1) {
        dfs(grid, target, i + 1, j, colorFlag, flag);
    }
    if (j > 0) {
        dfs(grid, target, i, j - 1, colorFlag, flag);
    }
    if (j < grid[0].length - 1) {
        dfs(grid, target, i, j + 1, colorFlag, flag);
    }

    flag[i][j] = false;
    isNotBoard(grid, target, i, j, colorFlag);
    return;
}

/**
 * 是否是边界：主要问题在于边界的判断
 *
 * @param row
 * @param col
 * @param colorFlag
 * @return
 */
private static void isNotBoard(int[][] grid, int target,
                               int row, int col, boolean[][] colorFlag) {

    /**
     * 网格第一行/列或最后一行/列都是边界
     */
    if (row == 0 || row == colorFlag.length - 1
            || col == 0 || col == colorFlag[0].length - 1) {
        colorFlag[row][col] = true;
        return;
    }
    /**
     * 4个方向相邻的都是边界或者都不是边界，说明该位置不是边界
     * 其他情况说明该位置是边界
     */
    boolean flag = (grid[row - 1][col] == target) && (grid[row][col - 1] == target)
            && (grid[row + 1][col] == target) && (grid[row][col + 1] == target);
    colorFlag[row][col] = !flag;
}

测试用例

public static void main(String[] args) {
    int[][] grid = new int[][]{{1, 1}, {1, 2}};
    int row = 0, col = 0;
    int color = 3;
    int[][] colorBoard = ColorBorder.colorBorder(grid, row, col, color);
    System.out.print("ColorBorder demo01 result : [");
    for (int i = 0; i < colorBoard.length; i++) {
        System.out.print("[");
        for (int j = 0; j < colorBoard[0].length; j++) {
            System.out.print("," + colorBoard[i][j]);
        }
        System.out.print("]");
    }
    System.out.println("]");

    grid = new int[][]{{1, 2, 2}, {2, 3, 2}};
    row = 0;
    col = 1;
    color = 3;
    colorBoard = ColorBorder.colorBorder(grid, row, col, color);
    System.out.print("ColorBorder demo02 result : [");
    for (int i = 0; i < colorBoard.length; i++) {
        System.out.print("[");
        for (int j = 0; j < colorBoard[0].length; j++) {
            System.out.print("," + colorBoard[i][j]);
        }
        System.out.print("]");
    }
    System.out.println("]");

    grid = new int[][]{{1, 1, 1}, {1, 1, 1}, {1, 1, 1}};
    row = 1;
    col = 1;
    color = 2;
    colorBoard = ColorBorder.colorBorder(grid, row, col, color);
    System.out.print("ColorBorder demo03 result : [");
    for (int i = 0; i < colorBoard.length; i++) {
        System.out.print("[");
        for (int j = 0; j < colorBoard[0].length; j++) {
            System.out.print("," + colorBoard[i][j]);
        }
        System.out.print("]");
    }
    System.out.println("]");

    grid = new int[][]{{1, 2, 1, 2, 1, 2}, {2, 2, 2, 2, 1, 2}, {1, 2, 2, 2, 1, 2}};
    row = 1;
    col = 3;
    color = 1;
    colorBoard = ColorBorder.colorBorder(grid, row, col, color);
    System.out.print("ColorBorder demo04 result : [");
    for (int i = 0; i < colorBoard.length; i++) {
        System.out.print("[");
        for (int j = 0; j < colorBoard[0].length; j++) {
            System.out.print("," + colorBoard[i][j]);
        }
        System.out.print("]");
    }
    System.out.println("]");

    grid = new int[][]{{1, 2, 2}, {2, 1, 2}, {1, 2, 3}, {3, 2, 1}};
    row = 1;
    col = 1;
    color = 3;
    colorBoard = ColorBorder.colorBorder(grid, row, col, color);
    System.out.print("ColorBorder demo05 result : [");
    for (int i = 0; i < colorBoard.length; i++) {
        System.out.print("[");
        for (int j = 0; j < colorBoard[0].length; j++) {
            System.out.print("," + colorBoard[i][j]);
        }
        System.out.print("]");
    }
    System.out.println("]");

    grid = new int[][]{{2, 1, 3, 2, 1, 1, 2},
            {1, 2, 3, 1, 2, 1, 2},
            {1, 2, 1, 2, 2, 2, 2},
            {2, 1, 2, 2, 2, 2, 2},
            {2, 3, 3, 3, 2, 1, 2}};
    row = 4;
    col = 4;
    color = 3;
    //{{2,1,3,2,1,1,3},{1,2,3,1,3,1,3},{1,2,1,3,2,3,3},{2,1,3,3,2,3,3},{2,3,3,3,3,1,3}}
    colorBoard = ColorBorder.colorBorder(grid, row, col, color);
    System.out.print("ColorBorder demo06 result : [");
    for (int i = 0; i < colorBoard.length; i++) {
        System.out.print("[");
        for (int j = 0; j < colorBoard[0].length; j++) {
            System.out.print("," + colorBoard[i][j]);
        }
        System.out.print("]");
    }
    System.out.println("]");
}

运行结果

ColorBorder demo01 result : [[,3,3][,3,2]]
ColorBorder demo02 result : [[,1,3,3][,2,3,3]]
ColorBorder demo03 result : [[,2,2,2][,2,1,2][,2,2,2]]
ColorBorder demo04 result : [[,1,1,1,1,1,2][,1,2,1,1,1,2][,1,1,1,1,1,2]]
ColorBorder demo05 result : [[,1,2,2][,2,3,2][,1,2,3][,3,2,1]]
ColorBorder demo06 result : [[,2,1,3,2,1,1,3][,1,2,3,1,3,1,3][,1,2,1,3,2,3,3][,2,1,3,3,2,3,3][,2,3,3,3,3,1,3]]