在c ++中添加两个c字符串

Question

In my code I am trying to add two strings together, however for some reason I can't seem to get the correct return type for my stringAdd function. I want to be able to return a c-string. And my implementation doesn't seem to work either. Any suggestions?

 #include <iostream>
 #include<cstring>

 using namespace std;
 int stringLength(char *); // Function prototype 
 char stringAdd(char *strPtr, char *strPtr2);//Function prototype

int main()
{
   const int SIZE = 51; // Array size 
   char letter; // The character to count 
   char word1[SIZE] = "Happy ";
   char word2[SIZE] = "Birthday";

   cout <<"Your first c-string is: "<<word1<<"Your second c-string is: "<<word2<<"\n";
   cout << "The length of your first c-string is: ";

   cout << stringLength(word1) << " chars long.\n";
   cout << "The length of your second c-string is: ";

   cout << stringLength(word2) << " chars long.\n";

   if (SIZE >= (stringLength(word1) + stringLength(word2) + 1))
   {
      cout << "we are gunna add ur strings";
      stringAdd(word1, word2);
   }
   else
   {
      cout << "String1 is not large enough for both strings.\n";
   }
   return 0;
}

int stringLength(char *strPtr)
{
    int times = 0; // Number of times a char appears in the string 

    // Step through the string each char. 
    while (*strPtr != '\0')
    {
        if (*strPtr != '0') // If the current character doesnt equals the null terminator... 
           times++; // Increments the counter 
        strPtr++; // Goes to the next char in the string. 
    }
    return times;
}

Up until this point my code works fine however the function below doesn't seem to work at all. I'm not sure how I can add two c-strings using reference

char stringAdd(char *strPtr, char *strPtr2)
{
   int size1;
   int size2;
   size1= stringLength(strPtr);
   int j=size1+1; // counter set to the num of chars in the first c-string
   int i = 0; // counter for to add to the 2nd c-string
   size2= stringLength(strPtr2);
   size1=+size2;
   char newWord[size1];

   for(int i=0;i<size1;i++)
      newWord[i] = *strPtr[i]
   for(int j=0;j<size2;j++)
      newWord[i]= *str
}

Answer 1

Firstly, use std::string .

Then, use std::string .

Finally, if you really really must manipulate char arrays manually, then at least use the C standard library functions so you have a hope of getting null-termination right. The function you're looking for is std::strcat , which concatenates two strings.

After that, use std::string .

Answer 2

You have a typo in stringAdd that causes a bug

size1=+size2;

This should be

size1 += size2;

Otherwise you're simply overwriting size1 with the value of size2 . That being said, in C++ you aren't allowed to do this either

char newWord[size1];

The size of an array must be known at compile time not run time .

Answer 3

Function stringAdd is incorrect and has undefined behavior because it returns nothing.

Also this if statement in function stringLength

if (*strPtr != '0') // If the current character doesnt equals the null terminator... 

    times++; // Increments the counter 

doea not make great sense because the condition in the enclosing while statement

while (*strPtr != '\0')

is the same as in the if statement.

{

The functions can be written the following way

size_t stringLength( const char *strPtr )
{
    size_t n = 0;

    while ( strPtr[n] ) ++n;

    return n;
}


char * stringAdd( char *strPtr, const char *strPtr2 )
{
    char *p = strPtr + stringLength( strPtr );

    while ( *p++ = *strPtr2++ );

    return strPtr;
}

And in main you could write

if (SIZE >= (stringLength(word1) + stringLength(word2) + 1)) {
    cout << "we are gunna add ur strings" << endl;
    cout << stringAdd(word1, word2) << endl;
}
//...

In this case word2 would be appended to word1.

Answer 4

You have tagged this as "c++" and "c-strings", which is kind of like asking for a car that is powered by foot-power.

You have 2 options:

1. Use C++ strings
2. Use C strings

For the former:

#include <iostream>
#include <string>

int main()
{
    std::string word1 = "Happy";
    std::string word2 = "Birthday";
    // ... your other stuff
    std::string result = word1 + " " + word2 + "!";
    std::cout << "Result is " << result << std::endl;
    return 0;
}

For the latter:

#include <iostream> // if you are stuck using c-strings, this is kind of odd
#include <cstring>
#include <memory>

int main()
{
    const char* word1 = "Happy";
    const char* word2 = "Birthday";
    const unsigned int newWordSize = 20; // you only need 16 for this, so 20 is sufficient
    char newWord[newWordSize];
    std::memset(newWord, newWordSize, 0);
    std::strcpy(newWord, word1);
    std::strcat(newWord, " ");
    std::strcat(newWord, word2);
    std::strcat(newWord, "!");
    std::cout << "New Word is " << newWord << std::endl;
    return 0;
}

Why what you are doing is wrong:

// NOTE:  If your null-terminators are not set, this breaks as it is an infinite loop.
int stringLength(char *strPtr)
{
    // NOTE:  pointer arithmetic can speed up this function, and make this variable unnecessary
    int times = 0; // Number of times a char appears in the string 

    // Step through the string each char. 
    while (*strPtr != '\0')
    {
        if (*strPtr != '0') // If the current character doesnt equals the null terminator... 
           times++; // Increments the counter 
        strPtr++; // Goes to the next char in the string. 
    }
    return times;
}

char stringAdd(char *strPtr, char *strPtr2) // ERROR:  your return value should probably be char*, and you will need to free that memory later
{
   int size1;
   int size2;
   size1= stringLength(strPtr);
   int j=size1+1; // counter set to the num of chars in the first c-string
   int i = 0; // counter for to add to the 2nd c-string
   size2= stringLength(strPtr2);
   size1=+size2;
   char newWord[size1]; // ERROR:  you cannot allocate a dynamic array this way.

   for(int i=0;i<size1;i++) // ERROR:  you've set size1 = size1 + size2 + 1, and you attempt to access the first word with this new size.  You will access memory outside the bounds of your array
      newWord[i] = *strPtr[i]
   for(int j=0;j<size2;j++)
      newWord[i]= *str
    // ERROR:  You do not set the null-terminator for the new string
    // ERROR:  you do not return anything
}