JZ-C-12

剑指offer第十二题：打印1到最大的n个数，"大数问题"

//============================================================================
// Name        : JZ-C-12.cpp
// Author      : Laughing_Lz
// Version     :
// Copyright   : All Right Reserved
// Description : 剑指offer第十二题：打印1到最大的n个数，"大数问题"
//============================================================================

#include <iostream>
#include <string.h>
#include  <memory>//memory是C++空间配置器以及new delete定义的头文件，里面定义了空间配置器，new delete以及一些用于调用构造函数的函数。
using namespace std;

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

void Print1ToMaxOfNDigits_1(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;
}
// 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] = '';

    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);//打印，结束一次循环
        return;
    }

    for (int i = 0; i < 10; ++i) {
        number[index + 1] = i + '0';//可以将整数转成字符
        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]);
            cout << number[i];
        }
    }

//printf("	");
    cout << " ";
}

// ====================测试代码====================
void Test(int n) {
//printf("Test for %d begins:
", n);
    cout << "Test for " << n << " begins:" << endl;
    Print1ToMaxOfNDigits_1(n);
//    Print1ToMaxOfNDigits_2(n);

//printf("Test for %d ends.
", n);
    cout << endl << "Test for " << n << " ends." << endl;
}

int main(int argc, char **argv) {
    Test(1);
    Test(2);
    Test(3);
    Test(0);
    Test(-1);
    return 0;
}