C language-pointer exercises, pointer exercises

C language-pointer exercises, pointer exercises

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To better understand several difficult concepts in pointers:Pointer array, array pointer, function pointer, pointer function, use function pointer callback function.

1. Use a pointer array to initialize with an indefinite string. The last string ends with @ and outputs all strings and deletes the last @ character.

For example:

Input: aaaaa bbbbb abcdefg asdf @

Output:

Aaaaa

Bbbbb

Abcdefg

Asdf

1 # include <stdlib. h> 2 # include <string. h> 3 int main (int args, const char * argv []) 4 {5 char * p [10] = {NULL}; 6 int cnt = 0; // record the number of input strings 7 // apply for heap memory space 8 for (int I = 0; I <10; I ++) 9 {10 // apply for a memory space of 100 char Types 11 p [I] = (char *) malloc (100 * sizeof (char )); 12 // judge that the application is successful 13 if (! P [I]) 14 {15 return-1; 16} 17 scanf ("% s", p [I]); 18 cnt ++; 19 // determine whether the last character of the string is '@' yes: the replacement bits '\ 0' 20 int len = (int) strlen (p [I]); 21 if (* (p + I) + (len-1) = '@') 22 {23 * (p + I) + (len-1 )) = '\ 0'; 24} 25 // if (p [I] [len-1] = '@') 26 // {27 // p [I] [len-1] = '\ 0'; 28 //} 29 // when a single character bit' \ n' is read, skip loop 30 if (getchar () = '\ n') 31 {32 break; 33} 34} 35 36 for (int I = 0; I <cnt; I ++) 37 {38 printf ("% s \ n", p [I]); 39} 40 return 0; 41}

2.

Function pointer callback

Define three functions at will, use the function pointer to call the three functions, input a n, print n times the Function

1 # include <stdlib. h> 2 # include <string. h> 3 void p_world (void) 4 {5 printf ("world \ n"); 6} 7 void p_hello (void) 8 {9 printf ("hello \ n "); 10} 11 void p_welcome (void) 12 {13 printf ("welcome \ n "); 14} 15 // use the function pointer to call back the above three functions 16 void print (void (* pfunc) (void), int cnt) 17 {18 for (int I = 0; I <cnt; I ++) 19 {20 pfunc (); 21} 22} 23 int main () 24 {25 int n = 0; 26 printf ("Callback times: "); 27 scanf (" % d ", & n); 28 // declare a pointer array to store the function name (Function Location Address) 29 void * pf [3] = {p_world, p_hello, p_welcome}; 30 char * str [3] = {"p_world", "p_hello", "p_welcome "}; 31 char * inputstr = NULL; 32 inputstr = (char *) malloc (100 * sizeof (char); 33 if (! Inputstr) 34 {35 return-1; 36} 37 printf ("callback function name:"); 38 scanf ("% s", inputstr ); 39 for (int I = 0; I <3; I ++) 40 {41 if (! Strcmp (str [I], inputstr) 42 {43 print (pf [I], n); 44} 45} 46 // release memory space 47 free (inputstr ); 48 inputstr = NULL; 49 return 0; 50}View Code