实现数字型字符串的加法运算

实现数字型字符串的加法运算

如输入字符串num1=”1234”, num2=”234”,输出”1468”;num1=”1234”, num2=”-234”,输出”1000”;可实现高精度运算

代码实现

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

void
reverseStr(char* str)
{
    int ii = 0;
    int len = strlen(str);
    char temp;

    for (ii = 0; ii < len/2; ii++)
    {
        temp = str[len-1-ii];
        str[len-1-ii] = str[ii];
        str[ii] = temp;
    }
    return;
}

void
delFirststzero(char* str)
{
    int is_neg = 0;
    int len = strlen(str);
    char* p_str = str + len - 1;
    int ii = len - 1;

    reverseStr(str);
    if (*p_str == '-')
    {
        *p_str = 0;
        is_neg = 1;
        p_str--;
        ii--;
    }

    for (; ii > 0; ii--)
    {
        if (*p_str != '0')
        {
            if (is_neg)
            {
                *(p_str+1) = '-';
            }
            break;
        }
        *p_str = 0;
        p_str--;
    }
    reverseStr(str);
    return;
}

void
add(const char* num1, const char* num2, char* resault)
{
    char* p_num1 = NULL;
    char* p_num2 = NULL;
    char* p_num1_temp = NULL;
    char* p_num2_temp = NULL;
    char* p_temp = NULL;
    char* p_res = resault;
    char temp;
    int len1 = 0;
    int len2 = 0;
    int max_len = 0;
    int ii = 0;
    int cmp_flag = 0;
    int res_neg = 0;

    if (!num1 || !num2 || !resault)
    {
        return;
    }

    len1 = strlen(num1);
    len2 = strlen(num2);

    if (num1[0] == '-')
    {
        len1--;
    }
    if (num2[0] == '-')
    {
        len2--;
    }
    max_len = (len1 > len2) ? len1 : len2;
    p_num1 = (char*)malloc((max_len + 1) * sizeof(char));
    p_num2 = (char*)malloc((max_len + 1) * sizeof(char));
    if (!p_num1 || !p_num2)
    {
        return;
    }
    p_num1_temp = p_num1;
    p_num2_temp = p_num2;
    memset(p_num1, 0, (max_len + 1) * sizeof(char));
    memset(p_num2, 0, (max_len + 1) * sizeof(char));
    memcpy(p_num1, (num1[0] == '-') ? num1 + 1 : num1, len1 * sizeof(char));
    memcpy(p_num2, (num2[0] == '-') ? num2 + 1 : num2, len2 * sizeof(char));
    reverseStr(p_num1);
    reverseStr(p_num2);

    ii = (len1 > len2) ? len2 : len1;
    p_temp = (len1 > len2) ? (p_num2 + len2) : (p_num1 + len1);
    while(ii < max_len)
    {
        *p_temp++ = '0';
        ii++;
    }
    p_temp = NULL;
    ii = 0;

    if ((num1[0] != '-' && num2[0] != '-') || (num1[0] == '-' && num2[0] == '-'))
    {
        //do add
        *p_res = '0';
        while (ii < max_len)
        {
            temp = *p_res - '0';
            temp += (*p_num1 - '0' + *p_num2 - '0');
            *p_res++ = (temp % 10 + '0');
            *p_res = temp / 10 + '0';
            p_num1++;
            p_num2++;
            ii++;
        }
        if (num1[0] == '-' && num2[0] == '-')
        {
            if (*p_res > '0')
            {
                p_res++;
            }
            *p_res = '-';
        }
    }
    else
    {
        //do decrease
        if (len1 == len2)
        {
            cmp_flag = memcmp((num1[0] == '-') ? num1 + 1 : num1, (num2[0] == '-') ? num2 + 1 : num2, max_len * sizeof(char));
            if ( cmp_flag == 0)
            {
                *p_res = '0';
                return;
            }
            else if (cmp_flag > 0)
            {
                if (num1[0] == '-')
                {
                    res_neg = 1;
                }
            }
            else
            {
                if (num2[0] == '-')
                {
                    res_neg = 1;
                }
            }
        }
        else if (len1 > len2)
        {
            cmp_flag = 1;//num1 > num2
            if (num1[0] == '-')
            {
                res_neg = 1;
            }
        }
        else
        {
            cmp_flag = -1;//num1 < num2
            if (num2[0] == '-')
            {
                res_neg = 1;
            }
        }
        ii = 0;
        *p_res = '0';
        while (ii < max_len)
        {
            temp = *p_res - '0';
            if (cmp_flag > 0)
            {
                *p_res++ = ((*p_num1 >= *p_num2) ? (*p_num1 - *p_num2) : (*p_num1 + 10 - *p_num2)) + '0'; 
                if (*p_num1 < *p_num2)
                {
                    (*(p_num1+1))--;
                }
                p_num1++;
                p_num2++;
            }
            else
            {
                *p_res++ = ((*p_num2 >= *p_num1) ? (*p_num2 - *p_num1) : (*p_num2 + 10 - *p_num1)) + '0'; 
                if (*p_num2 < *p_num1)
                {
                    (*(p_num2+1))--;
                }
                p_num1++;
                p_num2++;
            }
            ii++;
        }
        if (res_neg)
        {
            *p_res = '-';
        }
    }
    reverseStr(resault);
    delFirststzero(resault);
    free(p_num1_temp);
    free(p_num2_temp);
    return;
}
int main(int argc, const char* argv[])
{
    char rlt[256] = {0};
    if (argc < 2)
    {
        return -1;
    }

    add(argv[1], argv[2], rlt);
    printf("%s\n", rlt);

    return 0;
}