string_arithmetic_add.c

#include<stdio.h>
#define MAX 100000
typedef struct
{
    int arr[MAX];
}NUMBER;

/* 读取数字字符串，并转为int数组保存 */
void read(NUMBER *add_num)
{
    int i,digit=0;
    char ch[101];
    scanf("%s",ch);
    while(ch[digit])
        digit++;
    for(i=0;i < MAX;i++)
    {
        digit--;
        if(digit >= 0)
            add_num->arr[i]=ch[digit]-'0';
        else
            add_num->arr[i]=0;
    }
}

/* 两个int数组从低为开始相机，注意累加 carry 值 */
void addition(NUMBER a,NUMBER b,NUMBER *add_res)
{
    int carry=0;
    int i,temp;
    for(i=0;i < MAX;i++)
    {
        temp=a.arr[i]+b.arr[i]+carry;
        add_res->arr[i]=temp % 10;
        carry=temp / 10;
    }
}

/* 从高为开始答应，最终的结果数组 */
void print(NUMBER *add_num)
{
    int i;
    for(i=MAX-1;add_num->arr[i]==0;i--);
    for(;i>=0;i--)
        printf("%d",add_num->arr[i]);
}

int main()
{
    NUMBER x,y,z;
    printf("enter two positive integers: \n");
    read(&x);
    read(&y);
    printf("addition result: ");
    addition(x,y,&z);
    print(&z);
    return 0;
}