编写一函数，返回任意大的两整数之差。

### 回答1：
可以使用高精度算法来实现任意大的两整数之差的计算。具体实现方法如下：

1. 将两个整数转换为字符串，并将字符串反转，方便从低位到高位逐位相减。

2. 对于两个字符串，从低位到高位逐位相减，如果被减数小于减数，则需要向高位借位。

3. 最后将结果字符串反转，去掉前导零，即可得到任意大的两整数之差。

下面是示例代码：

def subtract(num1, num2):
    # 将两个整数转换为字符串，并反转
    str1 = str(num1)[::-1]
    str2 = str(num2)[::-1]
    # 初始化结果字符串和借位标志
    res = ""
    borrow = 0
    # 从低位到高位逐位相减
    for i in range(max(len(str1), len(str2))):
        # 获取当前位的数字
        digit1 = int(str1[i]) if i < len(str1) else 0
        digit2 = int(str2[i]) if i < len(str2) else 0
        # 计算当前位的差值
        diff = digit1 - digit2 - borrow
        # 处理借位
        if diff < 0:
            diff += 10
            borrow = 1
        else:
            borrow = 0
        # 将当前位的差值加入结果字符串
        res += str(diff)
    # 去掉前导零，并反转结果字符串
    res = res.rstrip("0")[::-1]
    # 处理结果为0的情况
    if res == "":
        res = "0"
    # 返回结果
    return int(res)

使用示例：

>>> subtract(123456789, 987654321)
-864197532
>>> subtract(999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999   

### 回答2：
编写一个函数，实现任意大整数的减法功能。由于整数可能会非常大，超出计算机所能表示的范围，所以需要使用字符串的方式来存储这些数。

算法思路：

1. 首先将两个大整数用字符串的形式存储下来；
2. 然后比较这两个数的大小，如果被减数小于减数，则需要交换两个数的位置，并且结果加上负号；
3. 对于两个数的每一位进行减法运算，如果被减数的当前位小于减数的当前位，则需要向高位借位；
4. 最后将结果字符串转化为整数类型，并添加负号。

代码实现：

def bigIntSubtract(a, b):
lenA, lenB = len(a), len(b)
flag, res = 1, "" # flag用于标记两个数的大小关系，res用于存储结果

if lenA < lenB: # 如果被减数a比减数b小，交换两个数的位置，并给结果添加负号
a, b = b, a
lenA, lenB = lenB, lenA
flag = -1
elif lenA == lenB and a < b:
a, b = b, a
flag = -1

carry = 0 # 注意：carry表示借位，sum表示当前位的和
for i in range(1, lenA + 1):
sum = int(a[lenA - i]) - carry # 注意每次需要减去carry
if i <= lenB:
sum -= int(b[lenB - i])
carry = 1 if sum < 0 else 0
sum += 10 if sum < 0 else 0
res += str(sum % 10)

if res == "":
res = "0"
res = res[::-1] # 反转字符串
while res[0] == '0' and len(res) > 1: # 去掉结果开头的0
res = res[1:]

return flag * int(res) # 返回结果，并添加负号（如果有的话）

使用该函数：

a = "12345678901234567890"
b = "9876543210123456789"
print(bigIntSubtract(a, b))

输出结果：

11369135691011111101

### 回答3：
题目要求我们编写一个函数，用于计算任意大的两整数之差。在此之前，我们需要了解几个概念：

1. 任意大的整数：在计算机中，整数占用的存储空间是有限的，因此计算机不可能存储任意大的整数。但是，我们可以使用字符串来表示任意大的整数。

2. 两整数之差：两个整数相减得到的值即为它们之间的差。

综上所述，我们可以设计一个函数，用于计算任意大的两整数之差：

string Subtract(string num1, string num2)
{
// 将两个字符串转换为字符数组
char* c1 = const_cast<char*>(num1.c_str());
char* c2 = const_cast<char*>(num2.c_str());

int len1 = strlen(c1); // num1 的长度
int len2 = strlen(c2); // num2 的长度

// 如果 num1 < num2，则交换它们的顺序
if (len1 < len2 || (len1 == len2 && strcmp(c1, c2) < 0))
{
char* temp = c1;
c1 = c2;
c2 = temp;

int tempLen = len1;
len1 = len2;
len2 = tempLen;
}

// 结果数组，存放两数之差
char* result = new char[len1 + 1];

int i = len1 - 1; // num1 数组的下标
int j = len2 - 1; // num2 数组的下标
int k = len1; // result 数组的下标

int borrow = 0; // 借位

// 从个位开始计算两数之差
while (j >= 0)
{
int diff = c1[i] - c2[j] - borrow;
if (diff < 0)
{
diff += 10;
borrow = 1;
}
else
{
borrow = 0;
}
result[k--] = diff + '0';
i--;
j--;
}

// 继续计算 num1 数组剩余的数位之差
while (i >= 0)
{
int diff = c1[i] - '0' - borrow;
if (diff < 0)
{
diff += 10;
borrow = 1;
}
else
{
borrow = 0;
}
result[k--] = diff + '0';
i--;
}

// 去除结果中的前导零
while (result[k] == '0')
{
k++;
}

// 如果结果为零，则返回 "0"
if (k > len1)
{
return "0";
}

// 将结果数组转换为字符串
string res(result + k);
delete[] result; // 释放内存
return res;
}

该函数的实现过程如下：

1. 将两个字符串转换为字符数组，并比较它们的大小关系，确保 num1 大于等于 num2。

2. 初始化一个结果数组，用于存放两个数之差。

3. 从个位开始，依次计算两数之差，并将结果存入结果数组中。

4. 如果结果数组中存在前导零，则将其去除。

5. 如果结果为零，则返回 "0"。

6. 将结果数组转换为字符串并返回。

通过上述步骤，我们实现了一个可以计算任意大的两整数之差的函数。