我想在函数make2Darray中实现,以使2D数组中的元素与行号相对应。
已经给出了打印和释放代码的其他部分,因此无需担心。我只想碰一下make2Darray函数。但是,在该函数中,还给出了分配部分。因此,我要更改的唯一代码是更改2D数组中元素的部分。
int** make2Darray(int width, int height) {
int **a;
int i = 0;
int j = 0;
/*allocate memory to store pointers for each row*/
a = (int **)calloc(height, sizeof(int *));
if(a != NULL) {
/* allocate memory to store data for each row*/
for(i = 0; i < height; i++) {
a[i] = (int *)calloc(width, sizeof(int));
if(a[i] == NULL) {
/* clean up */
free2Darray(a, height);
return NULL; /*aborting here*/
}
}
}
/* from this point down is the part I implemented, all code above was
given*/
if (height < 0 && width < 0) {
for (i = 0; i < height; i++) {
for (j = 0; j < width; j++) {
a[i][j] = j;
}
}
}
return a;
}
假设2D数组中的元素对应于行号
如果高度= 4且宽度= 3
0 0 0
1 1 1
2 2 2
3 3 3
但是,我总是得到0,这是我得到代码时的默认设置
0 0 0
0 0 0
0 0 0
0 0 0
最佳答案
您在代码中有两个主要问题。
1)初始化2D数组的代码应在if块内
2)if (height < 0 && width < 0) {
是错误的-您要使用>
而不是<
尝试:
int** make2Darray(int width, int height) {
int **a;
int i = 0;
int j = 0;
/*allocate memory to store pointers for each row*/
a = (int **)calloc(height, sizeof(int *));
if(a != NULL) {
/* allocate memory to store data for each row*/
for(i = 0; i < height; i++) {
a[i] = (int *)calloc(width, sizeof(int));
if(a[i] == NULL) {
/* clean up */
free2Darray(a, height);
return NULL; /*aborting here*/
}
}
// Moved inside the if(a != NULL) {
/* from this point down is the part I implemented, all code above was
given*/
if (height > 0 && width > 0) { // Corrected this part
for (i = 0; i < height; i++) {
for (j = 0; j < width; j++) {
a[i][j] = j;
}
}
}
}
return a;
}
一些提示:
1)在功能开始时进行高度和宽度检查,例如:
if (height <= 0 || width <= 0) return NULL;
2)原型
make2Darray(int width, int height)
在我看来倒退了,因为我们通常在列数之前提到行数。我希望:make2Darray(int height, int width)
。我什至更喜欢用“行”代替“高度”,用“柱”代替“宽度”。3)您当前的代码在
if(a != NULL) {
内执行“所有实际工作”,这没关系,但是(对我而言)如果您改为使用if(a == NULL) return NULL;
,则代码(对我来说)会更清楚4)无需投放
calloc
通过这些更新,代码可能是:
int** make2Darray(int rows, int columns) {
int **a;
int i = 0;
int j = 0;
if (rows <= 0 || columns <= 0) return NULL;
a = calloc(rows, sizeof(int*));
if(a == NULL) return NULL;
/* allocate memory to store data for each row*/
for(i = 0; i < rows; i++) {
a[i] = calloc(columns, sizeof(int));
if(a[i] == NULL) {
/* clean up */
free2Darray(a, rows);
return NULL; /*aborting here*/
}
}
/* from this point down is the part I implemented, all code above was
given*/
for (i = 0; i < rows; i++) {
for (j = 0; j < columns; j++) {
a[i][j] = j;
}
}
return a;
}
关于c - 试图在C中更改2D数组中的元素,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/54475287/