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  1. #include <stdio.h>      /* For printf()             */
  2. #include <stdlib.h>     /* For malloc(), free()     */
  3. #include <string.h>     /* For strcat(), strlen()   */
  4.  
  5.  
  6. /*
  7.  * Concatenates input strings into a single string.
  8.  * Returns the pointer to the resulting string.
  9.  * The string memory is allocated with malloc(),
  10.  * so the caller must release it using free().
  11.  * The input string array must have NULL as last element.
  12.  * If the input string array pointer is NULL, 
  13.  * NULL is returned.
  14.  * On memory allocation error, NULL is returned.
  15.  */
  16. char * ConcatenateStrings(const char** strings)
  17. {
  18.     int i = 0;              /* Loop index               */
  19.     int count = 0;          /* Count of input strings   */
  20.     char * result = NULL;   /* Result string            */
  21.     int totalLength = 0;    /* Length of result string  */
  22.  
  23.  
  24.     /* Check special case of NULL input pointer. */
  25.     if (strings == NULL)
  26.     {
  27.         return NULL;
  28.     }
  29.  
  30.     /* 
  31.      * Iterate through the input string array,
  32.      * calculating total required length for destination string.
  33.      * Get the total string count, too.
  34.      */
  35.     while (strings[i] != NULL)
  36.     {
  37.         totalLength += strlen(strings[i]);
  38.         i++;
  39.     }
  40.     count = i;
  41.     totalLength++;  /* Consider NUL terminator. */
  42.  
  43.     /*
  44.      * Allocate memory for the destination string.
  45.      */
  46.     result = malloc(sizeof(char) * totalLength);
  47.     if (result == NULL) 
  48.     {
  49.         /* Memory allocation failed. */
  50.         return NULL;
  51.     }
  52.  
  53.     /*
  54.      * Concatenate the input strings.
  55.      */
  56.     for (i = 0; i < count; i++) 
  57.     {
  58.         strcat(result, strings[i]);
  59.     }
  60.  
  61.     return result;
  62. }
  63.  
  64. /*
  65.  * Tests the string concatenation function.
  66.  */
  67. int main(void)
  68. {
  69.     /* Result of string concatenation */
  70.     char * result = NULL;
  71.  
  72.     /* Some test string array */
  73.     const char * test[] = 
  74.     {
  75.         "Hello ",
  76.         "world",
  77.         "!",
  78.         " ",
  79.         "Ciao ",
  80.         "mondo!",
  81.         NULL                /* String array terminator */
  82.     };
  83.  
  84.     /* Try string concatenation code. */
  85.     result = ConcatenateStrings(test);
  86.  
  87.     /* Print result. */
  88.     printf("%s\n", result);
  89.  
  90.     /* Release memory allocated by the concatenate function. */
  91.     free(result);
  92.  
  93.     /* All right */
  94.     return 0;
  95. }
  96.  
Success #stdin #stdout 0s 2380KB
comments (?)
stdin 
Standard input is empty
stdout 
Hello world! Ciao mondo!
https://ideone.com/ZYM3MB
language:
C (gcc 8.3)
created:
10 years ago
visibility:
public

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