我按顺序对齐几个数组并执行某种分类。我创建了一个数组来保存其他数组,以简化我想要执行的操作。
可悲的是,当我运行它时我的程序崩溃了,我继续调试它,最后意识到sizeof
运算符给了我指针的大小而不是循环内的数组。所以我采用了繁琐的解决方案我的计划有效。
如何避免这种繁琐的方法?我想在一个循环内计算!
#include <iostream>
#include <string>
#define ARRSIZE(X) sizeof(X) / sizeof(*X)
int classify(const char *asset, const char ***T, size_t T_size, size_t *index);
int main(void)
{
const char *names[] = { "book","resources","vehicles","buildings" };
const char *books[] = { "A","B","C","D" };
const char *resources[] = { "E","F","G" };
const char *vehicles[] = { "H","I","J","K","L","M" };
const char *buildings[] = { "N","O","P","Q","R","S","T","U","V" };
const char **T[] = { books,resources,vehicles,buildings };
size_t T_size = sizeof(T) / sizeof(*T);
size_t n, *index = new size_t[T_size];
/* This will yeild the size of pointers not arrays...
for (n = 0; n < T_size; n++) {
index[n] = ARRSIZE(T[n]);
}
*/
/* Cumbersome solution */
index[0] = ARRSIZE(books);
index[1] = ARRSIZE(resources);
index[2] = ARRSIZE(vehicles);
index[3] = ARRSIZE(buildings);
const char asset[] = "L";
int i = classify(asset, T, T_size, index);
if (i < 0) {
printf("asset is alien !!!\n");
}
else {
printf("asset ---> %s\n", names[i]);
}
delete index;
return 0;
}
int classify(const char *asset, const char ***T, size_t T_size, size_t *index)
{
size_t x, y;
for (x = 0; x < T_size; x++) {
for (y = 0; y < index[x]; y++) {
if (strcmp(asset, T[x][y]) == 0) {
return x;
}
}
}
return -1;
}
答案 0 :(得分:4)
当你包括<string>
和<iostream>
时,我认为问题是关于C ++而不是C.为了避免所有这些复杂化,只需使用容器。 E.g:
#include <vector>
std::vector<int> vect = std::vector<int>(3,0);
std::cout << vect.size() << std::endl; // prints 3
答案 1 :(得分:2)
如果使用C编码,一种解决方案是使用特殊项目终止数组,例如NULL
const char *books[] = { "A","B","C","D", NULL };
size_t size(const char *arr[])
{
const char **p = arr;
while (*p)
{
p++;
}
return p - arr;
}
答案 2 :(得分:0)
您可以指定数组大小explizit:
size_t n, index[] = {ARRSIZE(books), ARRSIZE(resources), ARRSIZE(vehicles), ARRSIZE(vehicles)};
或者如果你想避免双重打字,你可以X-Macros推出所有内容:
#define TBL \
X(books) \
X(resources) \
X(vehicles) \
X(buildings)
const char **T[] = {
#define X(x) x,
TBL
};
#undef X
size_t n, index[] = {
#define X(x) ARRSIZE(x),
TBL
};
产生相同的。请参阅Running Demo。