leftover.cpp

采用vc++语言编写的该函数主要用于查看邮政编码的前指定位数的数位

//*************** 函数重载 *************//
//*****该函数用于查看邮政编码的前指定位数的数位******//

#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;
	}
	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;
}