C语言程序设计（现代方法）第二版，第九章编程题三和第八章编程题九两种跳出循环的解题思路

思路一：

#include 
#include 
#include 

#define N 10
void generate_random(char a[N][N]);
void print_array(char a[N][N]);
int main()
{
	char walk[N][N] = { 0 };

	generate_random(walk);

	print_array(walk);

	return 0;
}
void generate_random(char a[N][N])
{
	int row, column;
	for (row = 0;row < N;row++)
	{
		for (column = 0;column < N;column++)
		{
			a[row][column] = '.';
		}
	}

	srand((unsigned)time(NULL));

	int i = 0, n = 0, b = 0;
	row = 0;column = 0;
	a[0][0] = 'A';//a[0][0]作为起点
	int c = 'A';//变量c有自增的需要
	for (i;i < 25;)
	{
		
		n = rand() % 4;
		switch (n)
		{
		case 0:
			--row;//多次循环尽量不要用后自增，不易控制
			if (row >= 0 && a[row][column] == '.')
			{
				a[row][column] = ++c;
				i++;
				break;
			}
			row++;
			break;

		case 1:
			--column;
			if (column >= 0 && a[row][column] == '.')
			{
				a[row][column] = ++c;
				i++;
				break;
			}
			++column;
			break;

		case 2:
			++row;
			if (row < N && a[row][column] == '.')
			{
				a[row][column] = ++c;
				i++;
				break;
			}
			--row;
			break;

		case 3:
			++column;
			if (column < N && a[row][column] == '.')
			{
				a[row][column] = ++c;
				i++;
				break;
			}
			--column;
			break;
		}

		if (row - 1 < 0 || a[row - 1][column] != '.')
		{
			if (column - 1 < 0 || a[row][column - 1] != '.')
			{
				if (row + 1 > N - 1 || a[row + 1][column] != '.')
				{
					if (column + 1 > N - 1 || a[row][column + 1] != '.')
						break;//当周围4个点的位置都不满足条件时，break（我认为这样用级联是if语句更容易阅读）
				}
			}
		}
	}
}
void print_array(char a[N][N])
{
	int row, column;
	for (row = 0;row < N;row++)
	{
		for (column = 0;column < N;column++)
		{
			printf(" %c", a[row][column]);
		}
		printf("n");
	}
}

思路二：

#include 
#include 
#include 

#define N 10//第三题
void generate_random(char a[N][N]);
void print_array(char a[N][N]);
int main()
{
	char walk[N][N] = { 0 };

	generate_random(walk);

	print_array(walk);

	return 0;
}
void generate_random(char a[N][N])
{
	int row, column;
	for (row = 0;row < N;row++)
	{
		for (column = 0;column < N;column++)
		{
			a[row][column] = '.';
		}
	}

	srand((unsigned)time(NULL));

	int i = 0, n = 0, b = 0;
	row = 0;column = 0;
	a[0][0] = 'A';//a[0][0]作为起点
	int c = 'A';//变量c有自增的需要
	for (i;i < 25;)
	{
		b++;//用于检测程序的循环次数
		n = rand() % 4;
		switch (n)
		{
		case 0:
			--row;//多次循环尽量不要用后自增，不易控制
			if (row >= 0 && a[row][column] == '.')
			{
				a[row][column] = ++c;
				i++;
				break;
			}
			row++;
			break;

		case 1:
			--column;
			if (column >= 0 && a[row][column] == '.')
			{
				a[row][column] = ++c;
				i++;
				break;
			}
			++column;
			break;

		case 2:
			++row;
			if (row < N && a[row][column] == '.')
			{
				a[row][column] = ++c;
				i++;
				break;
			}
			--row;
			break;

		case 3:
			++column;
			if (column < N && a[row][column] == '.')
			{
				a[row][column] = ++c;
				i++;
				break;
			}
			--column;
			break;
		}

		if (b > 500) break;//完整的一次完成A-Z的循环，只需要循环70次左右，如果超过500次循环仍然没有
	}///跳出循环，那么有99.99999....的可能性是路走死了
}
void print_array(char a[N][N])
{
	int row, column;
	for (row = 0;row < N;row++)
	{
		for (column = 0;column < N;column++)
		{
			printf(" %c", a[row][column]);
		}
		printf("n");
	}
}