{

int result = 0;

bool isNegative = false;

int i = 0;

//check str is negative or not

if(str[0] == '-')

{

isNegative = true;

i++;

}

for(; i<str.size(); ++i)

{

if(std::isdigit(str[i]))

{

// to check the overflow is exist or not

// if INT_MAX > (result * 10 + (str[i] - '0')) then there is a overflow

// if(result * 10 + (str[i] - '0') > INT_MAX) // but this will not work

// because result * 10 + (str[i] - '0') if result is cause overflow then there

// will be undefined behaviour so it is good idea to compare it with result

if(result > (INT_MAX - (str[i] - '0')) / 10)

{

std::cout<<"overflow detected"<<std::endl;

return isNegative ? INT_MIN : INT_MAX;

}

result = result * 10 + (str[i] - '0');

}

else

return 0;

}

if(isNegative)

result = -result;

return result;

{

std::cout<<stringToInteger("123")<<std::endl;

std::cout<<stringToInteger("99999999999999999999999999");

std::endl(std::cout);

return 0;

}