cpp 8.9

8.9

#include<iostream>
const int ArSize = 80;
char *left(const char * str, int n = 1);
int main()
{
	using namespace std;
	char sample[ArSize];
	cout << "Enter a string:\n";
	cin.get(sample, ArSize);
	char*ps = left(sample, 4);
	cout << ps << endl;
	delete[] ps;
	ps = left(sample);
	cout << ps << endl;
	delete[] ps;

	system("pause");
	return 0;
}

char * left(const char * str, int n)
{
	if (n < 0)
		n = 0;
	char * p = new char[n + 1];
	int i;
	for (i = 0; i < n && str[i]; i++)
		p[i] = str[i];
	while (i <= n)
		p[i++] = '\0';
	return p;
}

8.10

#include<iostream>
unsigned long left(unsigned long num, unsigned ct);
char * left(const char * str, int n = 1);

int main()
{
	using namespace std;
	char * trip = "Hawaii!!";
	unsigned long n = 12345678;
	int i;
	char * temp;

	for (i = 1; i < 10; i++)
	{
		cout << left(n, i) << endl;
		temp = left(trip, i);
		cout << temp << endl;
		delete[] temp;
	}

	system("pause");
	return 0;
}

unsigned long left(unsigned long num, unsigned ct)
{
	unsigned digits = 1;
	unsigned long n = num;

	if (ct == 0 || num == 0)
		return 0;
	while (n /= 10)
		digits++;
	if (digits > ct)
	{
		ct = digits - ct;
		while (ct--)
			num /= 10;
		return num;
	}
	else
		return num;
}

char * left(const char * str, int n)
{
	if (n < 0)
		n = 0;
	char * p = new char[n + 1];
	int i;
	for (i = 0; i < n && str[i]; i++)
		p[i] = str[i];
	while (i <= n)
		p[i++] = '\0';
	return p;
}