03.11 home work

#include <iostream>
#include <string.h>

using namespace std;


char* copystr(char*);

char* phone_number(char*);
void char_change(char*, char, char);
bool pali_text(char*);
void delete_char(char*&, char);

int main()
{
    cout << "First exercise\n";
    //First exercise
    char s[] = "+38(099)714-55-12";
    cout << phone_number(s) << endl;

    cout << "Second exercise\n";
    //Second exercise
    char a[] = "fsdfsd fsdfsd fsdfewrf fsdfsdf";

    cout << a << endl;
    cout << endl;

    char_change(a, ' ', 9);

    cout << a << endl;
    cout << endl;

    cout << "Third exercise\n";
    //third exercise
    char b[] = "ababa";
    cout << pali_text(b) << endl;

    cout << "Last exercise \n";
    //last exercise

    char* z = copystr(a);
    delete_char(z, 'f');

    cout << z << endl;

}

char* copystr(char* str){
    char* tmp = nullptr;
    tmp = new char[strlen(str)+1];
    for(int i = 0; str[i] != '\0'; i++)
        tmp[i] = str[i];

    tmp[strlen(str)] = '\0';
    return tmp;
}

//first exercise
char* phone_number(char* string)
{
    char* tmp = new char[20];

    for(int i = 0, j = 0; string[i] != '\0'; i++)
    {
        if(isdigit(string[i]))
        {
            tmp[j] = string[i];
            j++;
        }
    }
    return copystr(tmp);
}

//secon exercise
void char_change(char* string, char in, char out)
{
    for(int i = 0; string[i] !='\0'; i++)
        if(string[i] == in) string[i] = out;
}
//third exercise
bool pali_text(char* string)
{
    for(int i = 0, j = strlen(string)-1; i <= strlen(string)/2;i++)
        if(string[i] != string[j-i])
            return false;
    return true;
}
//last exercise
void delete_char(char*& string, char chr)
{
    char* tmp = new char[100];

    for(int i = 0, j = 0; string[i] != '\0'; i++)
    {
        if(string[i] != chr)
        {
            tmp[j] = string[i];
            j++;
        }
    }

    delete[] string;

    string = copystr(tmp);
}