Modern atoi() example of using

#include <iostream>
#include <cstdlib>
using namespace std;
static const char MINUS = '-';
char* my_trimLeft(const char* src);
int my_atoi(const char*  src);
int main()
{
    cout << my_atoi("bjk vvh-)(-20856--fbhcfr f");
    cin.get();
    return 0;
}
// Implement the function, that transforms string into integer.
int my_atoi(const char*  src)
{
    bool isNegative = false;
    char* str = my_trimLeft(src);
    if(str == NULL)
    {
        return EXIT_FAILURE;            // input error, terminating
    }
    if(str[0] == MINUS)
    {
        isNegative = true;
        str++;
    }
    int result = 0;
    int digit = 1;
    const int DIGIT_DIFFERENCE = 10;
    const char ZERO_SYMBOL = '0';
    for(int i = (strlen(str)-1); i >= 0; i--)
    {
        result = result + (digit * int(str[i]-ZERO_SYMBOL));
        digit = digit * DIGIT_DIFFERENCE;
    }
    if(isNegative == false)
    {
        delete [] str;
        return result;
    }
    else
    {
        str--;
        delete [] str;
        return -result;
    }
}
char* my_trimLeft(const char* src)
{
    if(strlen(src) == 0)    // there's no string
    {
        return NULL;
    }
    char* resultStr = new char[strlen(src)];
    int srcIndex = 0;
    int resultIndex = 0;
    while(  (0 == isdigit(src[srcIndex]))
        &&
            (srcIndex < strlen(src))
        )
    {
        if ((src[srcIndex] == MINUS) && (0 != isdigit(src[srcIndex+1])))
        {
            resultStr[resultIndex] = MINUS;
            resultIndex++;
        }
        srcIndex++;
    }
    // now srcIndex indexes the first numeric in the string
    while(  (0 != isdigit(src[srcIndex]))
        &&
            (srcIndex < strlen(src))
        )
    {
        resultStr[resultIndex] = src[srcIndex];
        resultIndex++;
        srcIndex++;
    }
    resultStr[resultIndex] = '\0';
    if(resultIndex == 0)    // no numerics in the string
    {
        return NULL;
    }
    return resultStr;
}