实现字符串数字的乘法运算

实现字符串数字乘法运算

如输入11, 2 输出 22； 输入 -10， 2，输出-20

//实现字符串数字乘法运算

#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
mul(const char* num1, const char* num2, char* resault)
{
    const char* p_num1 = NULL;
    const char* p_num2 = NULL;
    const char* p_temp = NULL;
    char* p_res = resault;
    char temp;
    int len1 = 0;
    int len2 = 0;
    int ii = 0;
    int jj = 0;
    int res_neg = 0;

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

    len1 = strlen(num1);
    len2 = strlen(num2);
    p_num1 = num1 + len1 - 1;
    p_num2 = num2 + len2 - 1;

    if (num1[0] == '-')
    {
        len1--;
    }
    if (num2[0] == '-')
    {
        len2--;
    }


    if ((num1[0] != '-' && num2[0] != '-') || (num1[0] == '-' && num2[0] == '-'))
    {
        res_neg = 0;
    }
    else
    {
        res_neg = 1;
    }
    *p_res = '0';
    p_temp = p_num2;
    for (ii = 0; ii < len1; ii++, p_num1--)
    {
        p_res = resault + ii;
        p_num2 = p_temp;
        for (jj = 0; jj < len2; jj++, p_num2--)
        {
            temp = *p_res - '0';
            temp += (*p_num1 - '0') * (*p_num2 - '0');
            *p_res++ = temp % 10 + '0';
            *p_res = (*p_res) ? *p_res + temp / 10 : temp / 10  + '0';
        }
    }

    if (res_neg)
    {
        if (*p_res > '0')
        {
            p_res++;
        }
        *p_res = '-';
    }

    reverseStr(resault);
    delFirststzero(resault);
    return;
}


int main(int argc, const char* argv[])
{
    char rlt[256] = {0};
    if (argc < 2)
    {
        return -1;
    }

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

    return 0;
}