python/TangDou/XiTi/1097.cpp

#include <bits/stdc++.h>

#define N 10001
using namespace std;

/**
 * 功能：整数数组转为字符串，length为有效数字的长度
 * @param a
 * @param length
 * @return
 */
string IntArrayToStr(int a[], int length) {
    char buff[10], b[500];
    int i;
    b[0] = '\0';
    for (i = 0; i < length; i++) {
        sprintf(buff, "%d", a[i]);
        strcat(b, buff);
    }
    return b;
}

/**
 * 功能：高精度加法
 * @param a1
 * @param b1
 * @return
 */
string Add(char *a1, char *b1) {
    int a[N], b[N], c[N], i, x = 0;
    memset(a, 0, sizeof(a));
    memset(b, 0, sizeof(b));
    memset(c, 0, sizeof(c));
    int lena = strlen(a1);
    int lenb = strlen(b1);
    for (i = 0; i < lena; i++) a[lena - i] = a1[i] - 48; //注意，这里是反着放的
    for (i = 0; i < lenb; i++) b[lenb - i] = b1[i] - 48; //注意，这里是反着放的
    int lenc = 1;
    while (lenc <= lena || lenc <= lenb) {
        c[lenc] = a[lenc] + b[lenc] + x;   //两数相加
        x = c[lenc] / 10;
        c[lenc] %= 10;
        lenc++;
    }
    c[lenc] = x;
    if (c[lenc] == 0) lenc--;     //处理最高位

    //数组左移一位,此代码由黄海增加于2020-11-20
    for (i = 1; i <= lenc; i++) {
        c[i - 1] = c[i];
    }
    //将整数数组转为字符串
    return IntArrayToStr(c, lenc);
}

/**
 * 功能：高精度减法
 * @param n1
 * @param n2
 */
string Subtract(char *n1, char *n2) {
    int a[N], b[N], c[N], i;
    char n[N];
    bool needFuHao = false;
    memset(a, 0, sizeof(a));
    memset(b, 0, sizeof(b));
    memset(c, 0, sizeof(c));
    int lena = strlen(n1), lenb = strlen(n2);
    if (lena < lenb || (lena == lenb && strcmp(n1, n2) < 0))
        //strcmp()为字符串比较函数，当n1=n2时，返回0，
        //n1>n2时，返回正整数；n1<n2时返回负整数
        //比完大小后，发现被减数小于减数，就交换。
    {
        strcpy(n, n1);  //将n1数组的值完全赋值给n数组
        strcpy(n1, n2);
        strcpy(n2, n);
        swap(lena, lenb);  //这步不能忘
        //printf("-");  //别忘了输出负号
        needFuHao = true;
    }
    for (i = 0; i < lena; i++) a[lena - i] = int(n1[i] - '0');
    for (i = 0; i < lenb; i++) b[lenb - i] = int(n2[i] - '0');
    i = 1;
    while (i <= lena || i <= lenb) {
        if (a[i] < b[i])   //借位
        {
            a[i] += 10;
            a[i + 1]--;
        }
        c[i] = a[i] - b[i];
        i++;
    }
    int lenc = i;
    while (c[lenc] == 0 && lenc > 1) lenc--;    //最高位为0，则不输出

    //数组左移一位,此代码由黄海增加于2020-11-20
    for (i = 1; i <= lenc; i++) {
        c[i - 1] = c[i];
    }
    //将整数数组转为字符串
    return needFuHao ? "-" + IntArrayToStr(c, lenc) : IntArrayToStr(c, lenc);
}

//高精度乘法
string Multi(char *a1, char *b1, int lena, int lenb) {
    int a[N], b[N], c[N], x;
    memset(a, 0, sizeof(a));
    memset(b, 0, sizeof(b));
    memset(c, 0, sizeof(c));
    for (int i = 0; i < lena; i++) a[lena - i] = a1[i] - 48;
    for (int i = 0; i < lenb; i++) b[lenb - i] = b1[i] - 48;
    for (int i = 0; i <= lena; i++) {
        x = 0;  //用来存放进位
        for (int j = 1; j <= lenb; j++) {
            c[i + j - 1] += a[i] * b[j] + x;
            x = c[i + j - 1] / 10;
            c[i + j - 1] %= 10;
        }
        c[i + lenb] = x;         //进位
    }
    int lenc = lena + lenb;
    while (c[lenc] == 0 && lenc > 1) lenc--;   //删除前导0
    //数组左移一位,此代码由黄海增加于2020-11-20
    for (int i = 1; i <= lenc; i++) {
        c[i - 1] = c[i];
    }
    //将整数数组转为字符串
    return IntArrayToStr(c, lenc);
}

int main() {
    //接收操作数
    char a1[N];
    char b1[N];
    cin >> a1 >> b1;
    //高精度加法
    string sum = Add(a1, b1);
    cout << sum << endl;
    //高精度减法
    string dec = Subtract(a1, b1);
    cout << dec << endl;
    //高精度乘法
    string result = Multi(a1, b1, strlen(a1), strlen(b1));
    cout << result << endl;
    return 0;
}