Java实现二维数组拆分为四个子数组的方法咨询

需求说明 #

输入4x4二维数组：

1 5 6 2
3 1 6 5
6 3 9 4
3 8 4 2

期望拆分输出四个2x2子数组：

1 5
3 1

6 2
6 5

6 3
3 8

9 4
4 2

实现建议 #

你计划通过创建四个新二维数组填充后打印的思路是可行的，以下是具体优化与实现步骤：

1. 先处理输入校验与尺寸计算 #

首先要确保输入是行列数相等的偶数方阵，避免非法输入导致异常；然后计算子数组的尺寸halfSize = grid.length / 2。

2. 初始化子数组并修正拼写错误 #

你代码里的BottonRight是拼写错误，应改为BottomRight，直接按子数组尺寸初始化四个数组：

int halfSize = grid.length / 2;
double[][] topLeft = new double[halfSize][halfSize];
double[][] topRight = new double[halfSize][halfSize];
double[][] bottomLeft = new double[halfSize][halfSize];
double[][] bottomRight = new double[halfSize][halfSize];

3. 高效填充子数组 #

可以用System.arraycopy替代嵌套循环填充，代码更简洁且效率更高：

// 填充左上区域
for (int i = 0; i < halfSize; i++) {
    System.arraycopy(grid[i], 0, topLeft[i], 0, halfSize);
}
// 填充右上区域
for (int i = 0; i < halfSize; i++) {
    System.arraycopy(grid[i], halfSize, topRight[i], 0, halfSize);
}
// 填充左下区域
for (int i = halfSize; i < grid.length; i++) {
    System.arraycopy(grid[i], 0, bottomLeft[i - halfSize], 0, halfSize);
}
// 填充右下区域
for (int i = halfSize; i < grid.length; i++) {
    System.arraycopy(grid[i], halfSize, bottomRight[i - halfSize], 0, halfSize);
}

4. 复用打印逻辑避免重复代码 #

单独写一个打印子数组的方法，减少冗余代码：

private static void printSubArray(double[][] subArr) {
    for (double[] row : subArr) {
        for (double num : row) {
            System.out.print(num + " ");
        }
        System.out.println();
    }
}

5. 调用打印方法输出结果 #

在splitGrid方法中调用打印逻辑，每个子数组后添加空行分隔：

printSubArray(topLeft);
System.out.println();
printSubArray(topRight);
System.out.println();
printSubArray(bottomLeft);
System.out.println();
printSubArray(bottomRight);

完整修改后的代码 #

public class problem {
    public static void main(String[] args) {
        double[][] array1 = { {1, 5, 6, 2}, 
                              {3, 1, 6, 5}, 
                              {6, 3, 9, 4}, 
                              {3, 8, 4, 2} };
        
        splitGrid(array1);
    }
    
    public static void splitGrid(double[][] grid) {
        // 校验输入是否为偶数方阵
        if (grid.length == 0 || grid.length % 2 != 0 || grid[0].length != grid.length) {
            System.out.println("输入必须为行列数相等的偶数方阵");
            return;
        }
        
        int halfSize = grid.length / 2;
        // 初始化四个子数组
        double[][] topLeft = new double[halfSize][halfSize];
        double[][] topRight = new double[halfSize][halfSize];
        double[][] bottomLeft = new double[halfSize][halfSize];
        double[][] bottomRight = new double[halfSize][halfSize];
        
        // 填充左上区域
        for (int i = 0; i < halfSize; i++) {
            System.arraycopy(grid[i], 0, topLeft[i], 0, halfSize);
        }
        // 填充右上区域
        for (int i = 0; i < halfSize; i++) {
            System.arraycopy(grid[i], halfSize, topRight[i], 0, halfSize);
        }
        // 填充左下区域
        for (int i = halfSize; i < grid.length; i++) {
            System.arraycopy(grid[i], 0, bottomLeft[i - halfSize], 0, halfSize);
        }
        // 填充右下区域
        for (int i = halfSize; i < grid.length; i++) {
            System.arraycopy(grid[i], halfSize, bottomRight[i - halfSize], 0, halfSize);
        }
        
        // 打印所有子数组
        printSubArray(topLeft);
        System.out.println();
        printSubArray(topRight);
        System.out.println();
        printSubArray(bottomLeft);
        System.out.println();
        printSubArray(bottomRight);
    }
    
    private static void printSubArray(double[][] subArr) {
        for (double[] row : subArr) {
            for (double num : row) {
                System.out.print(num + " ");
            }
            System.out.println();
        }
    }
}

内容的提问来源于stack exchange，提问作者MazaPan616