C language - left-handed string

Topic: Implement a function that can left-rotate k characters in a string

code:

Idea 1: Rotate 1 character each time, repeat k times

void left_move(char arr[], int k)
{
	int len = strlen(arr);
	k %= len;  //避免旋转次数超过字符串长度，重复旋转
	int i = 0;
	int j = 0;
	for (i = 0; i < k; i++)
	{
		char tmp = arr[0];
		for (j = 0; j < len - 1; j++)
		{
			arr[j] = arr[j + 1];
		}
		arr[j] = tmp;
	}
}

Idea 2: Divided into three steps: first, left-rotate k characters; second, left-rotate the rest of the characters; third, left-rotate the entire string

void reverse(char* left, char* right)
{
	while (left < right)
	{
		char tmp = *left;
		*left = *right;
		*right = tmp;
		left++;
		right--;
	}
}

void left_move(char arr[], int k)
{
	int len = strlen(arr);
	k %= len;
	//左部分
	reverse(arr, arr + k - 1);
	//右部分
	reverse(arr + k, arr + len - 1);
	//整体
	reverse(arr, arr + len - 1);
}

Idea 3: Assign the first k characters to the last k bits of the string, then mark the first k characters as '*', skip '*' and print the following characters directly when printing, the string needs to allocate enough space

void left_move(char* str, int k)
{
	int len = strlen(str);
	k %= len;
	for (int i = 0; i < k; i++)
	{
		*(str + len) = *str;
		*str = '*';
		str++;
	}
}

main function

int main()
{
	char arr[20] = "abcdef";
	int k = 0;
	scanf("%d", &k);
	left_move(arr, k);
	//printf("%s\n", arr);
	int len = strlen(arr);
	for (int i = 0; i < len; i++)
	{
		if (arr[i] != '*')
			printf("%c", arr[i]);
	}
	return 0;
}