用C++定义一个大整数类，能完成大整数的+-*/输入和输出

好的，我知道了。关于您的问题，可以使用结构体和字符数组来实现大整数的输入、输出、加减乘除等运算，具体实现如下：

#include <stdio.h>
#include <string.h>
#define MAXN 1000

typedef struct BigInteger {
    int len, s[MAXN];
    BigInteger() {
        memset(s, 0, sizeof(s));
        len = 1;
    }
    BigInteger(const char* num) {
        memset(s, 0, sizeof(s));
        int L = strlen(num);
        len = L;
        for (int i = 0; i < L; i++) s[i] = num[L - i - 1] - '0';
    }
    BigInteger operator=(const char* num) {
        memset(s, 0, sizeof(s));
        int L = strlen(num);
        len = L;
        for (int i = 0; i < L; i++) s[i] = num[L - i - 1] - '0';
        return *this;
    }
    BigInteger operator=(int num) {
        char s[MAXN];
        sprintf(s, "%d", num);
        *this = s;
        return *this;
    }
    BigInteger operator+(const BigInteger& b) const {
        BigInteger c;
        c.len = 0;
        for (int i = 0, g = 0; g || i < max(len, b.len); i++) {
            int x = g;
            if (i < len) x += s[i];
            if (i < b.len) x += b.s[i];
            c.s[c.len++] = x % 10;
            g = x / 10;
        }
        return c;
    }
    BigInteger operator-(const BigInteger& b) const {
        BigInteger c;
        c.len = 0;
        for (int i = 0, g = 0; i < len; i++) {
            int x = s[i] - g;
            if (i < b.len) x -= b.s[i];
            if (x >= 0) {
                g = 0;
            } else {
                g = 1;
                x += 10;
            }
            c.s[c.len++] = x;
        }
        while (c.len > 1 && c.s[c.len - 1] == 0) c.len--;
        return c;
    }
    BigInteger operator*(const BigInteger& b) const {
        BigInteger c;
        c.len = len + b.len;
        for (int i = 0; i < len; i++) {
            for (int j = 0; j < b.len; j++) {
                c.s[i + j] += s[i] * b.s[j];
            }
        }
        for (int i = 0; i < c.len - 1; i++) {
            c.s[i + 1] += c.s[i] / 10;
            c.s[i] %= 10;
        }
        while (c.len > 1 && c.s[c.len - 1] == 0) c.len--;
        return c;
    }
    BigInteger operator/(const BigInteger& b) const {
        BigInteger c;
        c.len = len - b.len + 1;
        if (c.len < 0) {
            c.len = 1;
            return c;
        }
        BigInteger temp = *this;
        for (int i = c.len - 1; i >= 0; i--) {
            BigInteger r("0");
            r.s[0] = temp.s[i + b.len];
            while (r >= b) {
                r = r - b;
                c.s[i]++;
            }
            c.s[i] = c.s[i] % 10;
            BigInteger t("1");
            t = t * pow(10, i);
            r = b * c.s[i];
            temp = temp - r * t;
        }
        while (c.len > 1 && c.s[c.len - 1] == 0) c.len--;
        return c;
    }
    bool operator<(const BigInteger& b) const {
        if (len != b.len) return len < b.len;
        for (int i = len - 1; i >= 0; i--) {
            if (s[i] != b.s[i]) return s[i] < b.s[i];
        }
        return false;
    }
    bool operator>(const BigInteger& b) const {
        return b < *this;
    }
    bool operator<=(const BigInteger& b) const {
        return !(b < *this);
    }
    bool operator>=(const BigInteger& b) const {
        return !(*this < b);
    }
    bool operator!=(const BigInteger& b) const {
        return b < *this || *this < b;
    }
    bool operator==(const BigInteger& b) const {
        return !(b < *this) && !(b > *this);
    }
    void print() {
        for (int i = len - 1; i >= 0; i--) printf("%d", s[i]);
    }
} BIGINT;

int main() {
    char num1[MAXN], num2[MAXN];
    scanf("%s%s", num1, num2);
    BIGINT a(num1), b(num2);
    printf("a - b = ");
    (a - b).print();
    printf("\na * b = ");
    (a * b).print();
    printf("\na / b = ");
    (a / b).print();
    printf("\n");
    return 0;
}

以上代码中，我们使用了结构体 `BigInteger` 代表大整数，其中 `s` 数组存储各位数字，`len` 表示整数位数。同时，我们还定义了加减乘除等运算符号，可以直接使用。