面试题12之打印1到最大的n位数_Print1ToMaxOfNDigits.cpp

// Print1ToMaxOfNDigits.cpp : Defines the entry point for the console application.
//

// 《剑指Offer——名企面试官精讲典型编程题》代码
// 著作权所有者：何海涛

#include "stdafx.h"
#include <memory>

void PrintNumber(char* number);
bool Increment(char* number);
void Print1ToMaxOfNDigitsRecursively(char* number, int length, int index);

// ====================方法一====================
void Print1ToMaxOfNDigits_1(int n)
{
    if(n <= 0)
        return;
 
    char *number = new char[n + 1];
    memset(number, '0', n);
    number[n] = '\0';
 
    while(!Increment(number))
    {
        PrintNumber(number);
    }
 
    delete []number;
}
 
// 字符串number表示一个数字，在 number上增加1
// 如果做加法溢出，则返回true；否则为false
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;
}

// ====================方法二====================
void Print1ToMaxOfNDigits_2(int n)
{
    if(n <= 0)
        return;
 
    char* number = new char[n + 1];
    number[n] = '\0';
 
    for(int i = 0; i < 10; ++i)
    {
        number[0] = i + '0';
        Print1ToMaxOfNDigitsRecursively(number, n, 0);
    }
 
    delete[] number;
}
 
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);
    }
}

// ====================公共函数====================
// 字符串number表示一个数字，数字有若干个0开头
// 打印出这个数字，并忽略开头的0
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("\t");
}

// ====================测试代码====================
void Test(int n)
{
    printf("Test for %d begins:\n", n);

    Print1ToMaxOfNDigits_1(n);
    Print1ToMaxOfNDigits_2(n);

    printf("Test for %d ends.\n", n);
}

int _tmain(int argc, _TCHAR* argv[])
{
    Test(1);
    Test(2);
    Test(3);
    Test(0);
    Test(-1);

    return 0;
}