免費的免費動態內存（）

Question

#include <stdlib.h> 
#include <stdio.h> 
int main() { 
    char **last_names; 
    // last_names has been assigned a char * array of length 4. Each element of the array has 
    // been assigned a char array of length 20. 
    // 
    // All of these memory has been allocated on the heap. 
    // Free all of the allocated memory (hint: 5 total arrays). 


    return 0; 
} 

我知道free（）方法，這是我的方法;

free(*last_names); 
free(last_names); 

但事實並非如此。任何幫助將不勝感激

Answer 1

從你的代碼的描述猜測，您的內存分配將是：

last_names = malloc(4 * sizeof(char*)); 
for (int i = 0; i < 4; i++) 
    last_names[i] = malloc(20 * sizeof(char)); 

所以釋放應做如下：

for (int i = 0; i < 4; i++) 
    free(last_names[i]); 
free(last_names);