打印1到最大的n位数

#include <string.h>

#include <iostream>
using namespace std;

//利用case语句使字符++  
char CharPlus(char a)  
{  
    char b;  
    switch ( a )  
    {  
    case '0': b = '1';  break;  
    case '1': b = '2';  break;  
    case '2': b = '3';  break;  
    case '3': b = '4';  break;  
    case '4': b = '5';  break;  
    case '5': b = '6';  break;  
    case '6': b = '7';  break;  
    case '7': b = '8';  break;  
    case '8': b = '9';  break;  
    case '9': b = '0';  break;  
    default:  cout<<"error"<<endl;  
    }  
    return b;  
}  

bool Increment(char* numchar,int len)  
{  
    bool flag = false;  
    if ( numchar[0] == '9' )                        //用于判断越界情况处理      
        flag=true;
    for (len = len-1; len >= 0; len-- )             //从数字低位开始更新
    {  
        numchar[len] = CharPlus( numchar[len] );    //更新该位上的数字  
        if ( numchar[len] != '0' )                  //判断是否向高位进位,如果该为由9->0，则向高位进位
            break;  
        if ( flag && numchar[0]=='0' )              //数值最高位从'9'变为'0'时，数值溢出,结束递增
            return false;  
    }  
    return true;  
}  

//打印输出时，要符合一般习惯，把前面的0去掉,从左开始打印 
void PrintNum(char* numchar){  
    int i = 0;  
    bool flag = false;  
    while(numchar[i++] == '0');//找到数值从高位到低位第一个不为'0'的位置
    --i;  
    while ( numchar[i] != '\0' ){  
        cout<<numchar[i]; 
        i++;  
    }  
    cout<<endl;  
}  

void Print1ToMaxOfNDigits(int n){  
    if ( n <= 0 ){  
        cout<<n<<" is illegal"<<endl;  
        return;  
    }
    char * numchar = new char[n+1];  
    memset( numchar,'0',sizeof(char)*(n+1) );         
    numchar[n] = '\0';                  //先对字符串数组初始化  

    while ( Increment(numchar,n) )      //字符串数组++，如果已经是最大则返回false  
    {  
        PrintNum(numchar);              //打印出该数字  
    }  
    delete[] numchar;  
}  

int main(){
    Print1ToMaxOfNDigits(1);
}

void Print1ToMaxOfNDigitsRecursively(char* numchar, int length, int index)  
{  
    if ( index == length -1)  
    {  
        PrintNum(numchar);  
        return;  
    }  
    for ( int i = 0; i < 10; i++ )  
    {  
        numchar[index+1] = i +'0';  
        Print1ToMaxOfNDigitsRecursively(numchar, length, index+1);  
    }  

}  
void Print1ToMaxOfNDigits(int n)  
{  
    if ( n <= 0 )  
    {  
        cout<<n<<" is illegal"<<endl;  
        return;  
    }  
    char * numchar = new char[n+1];  
    numchar[n] = '\0';                  //先对字符串数组初始化  

    for ( int i = 0; i < 10; i++ )  
    {  
        numchar[0] = i + '0';  
        Print1ToMaxOfNDigitsRecursively(numchar,n,0);  
    }  

    delete[] numchar;  
}