在字符串中的特定字符之后添加字符（最多1个字符串，数组）

Question

I need to put * after every * in string

Input:*tret*ret*re*ter
Output:**tret**ret**re**ter

Well i have code that works but problem is that i can use only one string(array). And i used two.

#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include <string.h>

int main() {

    char x[256], y[256], z = 0;

    scanf("%s", x);

    for (char i = 0; i < strlen(x); i++) {

        y[z++] = x[i];

        if (x[i] == '*')
            y[z++] = '*';
    }

    y[z] = '\0';

    printf("%s\n", y);

    system("pause");
    return 0;
}

I will be thankful for any advice how to make it with only one string.

I even try but it makes soem chars disappear

int main() {

    char x[256], z = 0;

    scanf("%s", x);

    for (char i = 0; i < strlen(x); i++) {



        if (x[i] == '*') {
            x[++i] = '*';
        }
    }


    printf("%s\n",x);

    system("pause");
    return 0;
}

Answer 1

I will be thankful for any advice how to make it with only one string.

Algorithm

Count the number of occurrences of '*' --> star_count .

Note the length of the string --> length

Ensure length + star_count < 256, else buffer is too small.

Loop from the end to the beginning.

Set src to end of string. (The null character)

Set dest to end of src + star_count .

// ***

Set *dest = null character.

While not done ( src != beginning):
- Assign *dest = *src and decrement both pointers.
- Conditionally assign *dest = '*' , decrement dest .

---

@Ian Abbott offers a nice improvement. Loop until pointers match.

From ***

While dest > src
- Assign *dest = *src and decrement both pointers.
- Conditionally assign *dest = '*' , decrement dest .

Answer 2

First of all, you should wonder why only one single array. IMHO, if it is simpler with two arrays, stick there.

Next you use char as indexes. Please don't unless you have a strong reason to. A decent compiler should warn you because it can be a cause of hard to detect errors. For example, if you implementation uses signed 8 bits char, the max value is 127 and not 255. So if the string contains 128 characters and the terminating null, the loop for (char i = 0; i < strlen(x); i++) { is an endless one. Because 127+1 is likely to be -128 (undefined behaviour, but very common).

And as you know the size of the x array, you should use a limited scanf and test its return value:

if (scanf("%255s", x) != 1) {
    // process error
    ...
}

For the rest, @chux's answer gives you the only way to extend a string in place:

• scan it once to find its final size
• process it starting from the end

Answer 3

When you find an * character, you'll have to shift every byte after it to the right to make room for an additional * character. Below is one such implementation:

#include<stdio.h>
#include <string.h>

int main(void)
{
    char x[256] = {'\0'}; // NUL Terminate Every Character

    printf("Enter String: ");
    scanf("%s", x);

    for(int i = 0; i < strlen(x); i++)
    {
        if(x[i] == '*')
        {
            for(int j = strlen(x) + 1; j > i; j--)
                x[j] = x[j - 1]; // Shift Every Byte, Starting With Last, To Right
            x[++i] = '*';
        }   
    }

    printf("%s\n", x);
    return 0;
}

Execution

Enter String: *hi*buddy*
**hi**buddy**