/*******************************************************************
*《剑指Offer——名企面试官精讲典型编程题》C++代码
*
* htfeng
* 2018.09.28
*
* 面试题17: 打印从1到最大的n位数
* 题目：输入数字n，an顺序打印从1到最大的n位十进制数，比如输入3，
* 则打印出1、2、3一直到最大的三位数999。
*
* 分析：有一个陷阱，当n很大的时候，用int或者long long都会溢出，怎么办？
* 使用字符串存储数字
*******************************************************************/#include<iostream>using namespace std;bool Increment(char* number);
void PrintNumber(char* number);
void Print1ToMaxOfNdigitsRecursively(char* number, int length, int index);// 方法一
void PrintToMaxOfDigits(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;
}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 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 << "\t";
}// 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);}
}int main() {int n = 3;PrintToMaxOfDigits(n);Print1ToMaxOfNdigits_2(n);system("pause");return 0;
}