Question

How to concatenate two strings in C

Answer 1

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
char* concat(const char *s1, const char *s2);
  
int main(void)
{
    char s1[] = "c c++ c#";
    char s2[] = " java python";
 
    char* s = concat(s1, s2);
     
    puts(s);
     
    free(s);
  
    return 0;
}

char* concat(const char *s1, const char *s2) {
    char *result = (char *)malloc(strlen(s1) + strlen(s2) + 1);
     
    strcpy(result, s1);
    strcat(result, s2);
 
    return result;
}
  
  
   
/*
run:
     
c c++ c# java python
  
*/

 

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Answer 2

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
char* concat(const char *s1, const char *s2);
  
int main(void)
{
    char s1[] = "c c++ c#";
    char s2[] = " java python";
 
    char* s = concat(s1, s2);
     
    puts(s);
     
    free(s);
  
    return 0;
}

char* concat(const char *s1, const char *s2) {
    char *result = (char *)malloc(strlen(s1) + strlen(s2) + 1);
     
    sprintf(result, "%s %s", s1, s2);
 
    return result;
}
  
  
   
/*
run:
     
c c++ c# java python
  
*/

 

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Answer 3

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
char* concat(const char *s1, const char *s2);
  
int main(void)
{
    char s1[] = "c c++ c#";
    char s2[] = " java python";
 
    char* s = concat(s1, s2);
     
    puts(s);
     
    free(s);
  
    return 0;
}

char* concat(const char *s1, const char *s2) {
    size_t len1 = strlen(s1);
    size_t len2 = strlen(s2);
    
    char *result = (char *)malloc(len1 + len2 + 1);
     
    memcpy(result, s1, len1);
    result[len1] = ' ';
    memcpy(result + len1 + 1, s2, len2 + 1); // len2 + (1 -> for null)
 
    return result;
}
  
  
   
/*
run:
     
c c++ c# java python
  
*/

 

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