打印从1到最大的n位数.

输入数字n,按顺序从打印出从1到最大的n位十进制数.比如输入3,也就是最大的3位数是999,那么就打印1.2.3.---999;

方法1:非递归

#include "stdafx.h"
#include <iostream>
#include <exception>
using namespace std;
void PrintNumber(char* number)
{
    bool isBeginning0 = true;
    int nLength = strlen(number);
    for(int i = 0;i<nLength;++i)
    {
        if(isBeginning0&&number[i]!='0')
            isBeginning0 = false;
        if(!isBeginning0)
        {
            printf("%c",number[i]);
        }

    }
    printf("	");
}
bool Increment(char* number)
{
    bool isOverflow = false;
    int nTakeOver = 0;
    int nLength = strlen(number);
    for(int i = nLength-1;i>=0;i--){
        int nSum = number[i]-'0'+nTakeOver;
        if(i==nLength-1)
            nSum++;
        if(nSum>=10)
        {
            if(i==0)
                isOverflow=true;
            else
            {
                nSum -= 10;
                nTakeOver=1;
                number[i]='0'+nSum;

            }
        }
        else{
            number[i]='0'+nSum;
            break;
        }
    }
    return isOverflow;

}
void PrintToMaxOfNDigits(int n)
{
    if(n<=0)
        return;
    char *number = new char[n+1];
    memset(number,'0',n);
    number[n]='';
    while(!Increment(number))
    {
        PrintNumber(number);
    }
    delete []number;
}
int _tmain(int argc, _TCHAR* argv[])
{
    int n = 4;
PrintToMaxOfNDigits(n);
    return 0;
}

 方法2.递归法，全排列用递归表达，数字的每一位都可能是0-9中的一个数，然后设置下一位。递归结束的条件是我们已经设置了数字的最后一位.

#include "stdafx.h"
#include <iostream>
#include <exception>
using namespace std;
void PrintNumber(char* number)
{
    bool isBeginning0 = true;
    int nLength = strlen(number);
    for(int i = 0;i<nLength;++i)
    {
        if(isBeginning0&&number[i]!='0')
            isBeginning0 = false;
        if(!isBeginning0)
        {
            printf("%c",number[i]);
        }

    }
    printf("	");
}
void Print1ToMaxOfNDigitsRecursively(char* number,int length,int index)
{
    if(index==length-1)
    {
        PrintNumber(number);
        return;
    }
    for(int i = 0;i<10;++i)
    {
        number[index+1]=i+'0';
        Print1ToMaxOfNDigitsRecursively(number,length,index+1);
    }
}
void Print1ToMaxOfNDigits(int n)
{
    if(n<=0)
        return;
    char* number = new char[n+1];
    number[n]='';
    for(int i = 0;i<10;++i)
    {
        number[0]=i+'0';
        Print1ToMaxOfNDigitsRecursively(number,n,0);
    }
    delete[] number;

}
int _tmain(int argc, _TCHAR* argv[])
{
    int n = 4;
Print1ToMaxOfNDigits(n);
    return 0;
}