大数乘法

#define   _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include<stdlib.h>
#include<string.h>
//C语言声明变量需要加上stuct
//C语言结构内部不可以有函数
//C语言结构体没有公有，私有，继承

struct MyStruct
{
    int num1;
    int num2;
    




};
struct  MyStruct MyStruct1;

/// 加法，减法
/// 1234.567 ×12345.987
/// 15K+  除法，

//————————

void getbigdata(char *dataa,char* datab)
{
    int lengtha = strlen(dataa);
    int lengthb = strlen(datab);
    int *pres = (int *)malloc(sizeof(int)*(lengtha + lengthb));
    memset(pres, 0, sizeof(int)*(lengtha + lengthb));//初始化
    //累乘
    for (int i = 0; i < lengtha;i++)
    {
        for (int j = 0; j < lengthb;j++)
        {
            pres[i+j+1]+=(dataa[i] - ‘0‘)*(datab[j] - ‘0‘);
        }
    }
    //进位
    for (int i = lengtha + lengthb-1;i>=0;i--)
    {
        if (pres[i]>=10)//进位
        {
            pres[i - 1] += pres[i] / 10;//进位
            pres[i] %= 10;//取出个位数
        }

    }
    int i = 0;
    while (pres[i]==0)
    {
        i++;//恰好不为0的位置
    }
    char *lastres = malloc(sizeof(char)*(lengtha + lengthb));
    int j;
    for (j = 0; j < lengtha + lengthb; j++, i++)
    {
        lastres[j] = pres[i] + ‘0‘;
    }
    lastres[j] = ‘\0‘;
    printf("last结果=%s",lastres);




}





void main()
{
    char str1[100] = { 0 };
    char str2[100] = { 0 };
    scanf("%s%s", str1, str2);
    printf("str1=%s,str2=%s", str1, str2);//打印结果
    getbigdata(str1, str2);

    //strcpy(str1, "123123");

    system("pause");


}