剑指offer——面试题17：打印从1到最大的n位数

用字符串模拟加法：

#include"iostream"
#include"string.h"
using namespace std;

bool AddOne(char *number,int n);
void PrintNumber(char *number,int n);

void Print1ToN(int n)
{
    if(n<=0)
        return;
    char *number=new char[n+1];
    memset(number,'0',n);
    number[n]='';
    while(AddOne(number,n))
    {
        PrintNumber(number,n);
    }
    delete[] number;
}

bool AddOne(char *number,int n)
{
    bool isInRange=true;
    int carry=0;
    int iDigit;
    for(int i=n-1;i>=0;i--)
    {
        iDigit=number[i]-'0'+carry;
        if(i==n-1)
            iDigit++;
        if(iDigit>=10)
        {
            if(i==0)
                isInRange=false;
            else
            {
                carry=iDigit/10;
                iDigit%=10;
                number[i]=iDigit+'0';
            }
        }
        else
        {
            number[i]=iDigit+'0';
            break;
        }
    }
    return isInRange;
}

void PrintNumber(char *number,int n)
{
    bool firstNoZero=false;
    for(int i=0;i<n;i++)
    {
        if(!firstNoZero&&number[i]!='0')
        {
            firstNoZero=true;
        }
        if(firstNoZero)
            cout<<number[i];
    }
    cout<<endl;
}
int main()
{
    int n;
    while(cin>>n)
    {
        Print1ToN(n);
    }
    return 0;
}

 还可以用全排列的思想，递归调用去解决：

#include"iostream"
using namespace std;

void Print1ToNRecursively(int *number,int length,int index);
void PrintNumber(int *number,int n);

void Print1ToN(int n)
{
    int *number=new int[n];

    for(int i=0;i<10;i++)
    {
        number[0]=i;
        Print1ToNRecursively(number,n,0);
    }
}

void Print1ToNRecursively(int *number,int length,int index)
{
    if(index==length-1)
    {
        PrintNumber(number,length);
        return;
    }
    for(int i=0;i<10;i++)
    {
        number[index+1]=i;
        Print1ToNRecursively(number,length,index+1);
    }
}

void PrintNumber(int *number,int n)
{
    int i=-1;
    while(i<n&&number[++i]==0) continue;
    while(i<n) cout<<number[i++];
    cout<<endl;
}

int main()
{
    int n;
    while(cin>>n)
    {
        Print1ToN(n);
    }
    return 0;
}