[ ][ ] 和 if 语句在代码中不起作用

Question

我在下面的代码中遇到了一些关于 if 语句和二维数组的问题，我在下面声明：

int[][]image =
    {
        {0,0,2,0,0,0,0,0,0,0,0,2},
        {0,0,0,0,0,0,0,0,0,0,0,0},
        {0,0,5,5,5,5,5,5,5,5,0,0},
        {0,0,5,5,5,5,5,5,5,5,0,0},
        {0,0,5,5,5,5,5,5,5,5,0,0},
        {2,0,5,5,5,5,5,5,5,5,0,2},
        {0,0,5,5,5,5,5,5,5,5,0,0},
        {0,0,5,5,5,5,5,5,5,5,0,0},
        {0,0,5,5,5,5,5,5,5,5,0,0},
        {0,0,5,5,5,5,5,5,5,5,0,0},
        {0,0,0,0,0,0,0,0,0,0,0,0},
        {0,0,0,0,2,0,0,0,0,0,0,0}//assume this rectangular image
    };  

    int[][]smooth = new int[image.length][image[0].length]; //new array equal to image[][]

注意图片[][]。它是由一系列数字组成的二维数组。在它下面，我初始化了一个相同的数组：smooth[][]。 smooth[][] 的每个元素都被 8 个边界元素加上自身的数值平均值替换。

smooth[][] 中的边缘元素（数组外边界上的元素）不应更改。

我尝试用 if 语句来做到这一点，但只成功了一半。上边框和左边框的数字不变（r == 0 || c == 0），但下边框或右边框的任何数字都会变化成为平均值。

    //compute the smoothed value of non-edge locations in smooth[][]

    for(int r=0; r<image.length-1; r++)     
    {// x-coordinate of element

    for(int c=0; c<image[r].length-1; c++)      
    { //y-coordinate of element

    int sum1 = 0;//sum of each element's 8 bordering elements and itself



    if(r == 0 || c == 0 || r == (image[c].length) || c == (image[r].length))
        smooth[r][c] = image[r][c]; 

    else        
    {

        sum1 = image[r-1][c-1] + image[r-1][c] + image[r-1][c+1]    
        + image[r][c-1] + image[r][c] + image[r][c+1] +image[r+1][c-1] 
        + image[r+1][c] + image[r+1][c+1];

        smooth[r][c]= sum1 / 9; //average of considered elements becomes new elements

Answer 1

看来问题出在这里

if(r == 0 || c == 0 || r == (image[c].length) || c == (image[r].length))
    smooth[r][c] = image[r][c];

这是你在说单元格是否是边的地方 (r == 0 || c == 0 || ...) 但你犯了一个小错误。请记住最后一个元素是长度减一，例如 (... r == (image[c].length - 1) || c == (image[r].length - 1)).

炫酷的奖励视觉效果：

         (array.length) is this ─┐ (notice it doesn't exist)
  (array.length - 1) is this ─┐  │
                              v  v
     array | [x] [x] [x] [x] [x]
element is | 1st 2nd 3rd 4th 5th
  index is |  0   1   2   3   4

Edit: The below is all true but I was thrown off by your use of the word equal but moreso my hasty reading. Because it is true and correct I will leave it, but it is irrelevant to this question.

int[][]smooth = new int[image.length][image[0].length]; //new array equal to image[][]

这不是创建一个与其相等的新数组，而是创建一个具有相同大小的新数组。它将新数组中的所有元素初始化为 0，而不是你认为它在做什么。使用 System.arraycopy() 的一些 for 循环来正确复制。

Answer 2

您过早地停止了处理，因为您的 if 语句无法捕捉到右边界和下边界的情况。您的 for 循环条件：

for(int r=0; r<image.length-1; r++)     
{// x-coordinate of element

    for(int c=0; c<image[r].length-1; c++)      
    { //y-coordinate of element

在到达右列或底行之前停止处理。 0 的默认值恰好与由于所有零而存在的平均值相匹配。

通过更改 for 循环条件以包含右侧和底部边界情况，让您的 if 语句捕获边界情况 - 不要从长度中减去 1。

for(int r=0; r<image.length; r++)     
{// x-coordinate of element

    for(int c=0; c<image[r].length; c++)      
    { //y-coordinate of element

但是您必须正确测试您的 "on the right" 和 "on the bottom" 条件。从此处数组的 length 中减去一个。

if(r == 0 || c == 0 || r == (image[c].length - 1) || c == (image[r].length - 1))
    smooth[r][c] = image[r][c];

[ ][ ] 和 if 语句在代码中不起作用

[ ][ ] and if-statement not working in code

java

arrays

if-statement

2d