c_cpp 面试题17：打印从1到最大的Ñ位数

Posted 2021-05-14

#include <iostream>

using namespace std;

bool Increment(char* number);
void PrintNumber(char* number);

void Print1ToMaxOfNDigits(int n) {
	if (n <= 0)
		return;

	char* number = new char[n + 1];
	memset(number, '0', n);
	number[n] = '\0';

	while (!Increment(number)) {
		PrintNumber(number);
	}
}


//通过进位来判断是否到了最大的n位数
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;
}

//打印输出
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");
}


int main() {

	Print1ToMaxOfNDigits(3);

	getchar();
	return 0;
}

#include <iostream>

using namespace std;

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

void Print1ToMaxOfNDigits(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);
	}
}



//打印输出
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");
}


int main() {

	Print1ToMaxOfNDigits(3);

	getchar();
	return 0;
}