itoa()和atoi()函数实现

int my_atoi(char* src)
{
	int sign=1; //符号变量
	int sum=0;
	if('-'==*src)
	{
		sign=-1;
		src++;
	}
	else if('+'==*src)
	{
		sign=1;
		src++;
	}
	while(*src>='0'&&*src<='9')
	{
		sum=sum*10+*src-'0';
	    src++;
	}
    sum=sign*sum;
	return sum;
}

char* my_itoa(int num)
{
	int sign=1;
	if(num<0)
	{
		sign=-1;
	}
	num=sign*num;
    
	int n=CountNum(num);
	char* s=new char[n+1];
    int k=n;
	s
='\0';
	while(num>0)
	{
		s[--n]=num%10+'0';
		num=num/10;
	}
	
	return s;

}

//计算一个整数的位数
int CountNum(int num)
{
	int n=0;
	while(num>0)
	{
		n++;
		num=num/10;
	}
	return n;

}