Project Modules

/*
总结：
    1.不要忘了溢出
    2.单独处理最高位的加法更容易些。
summary:
    1.The overflow of addition of large numbers
    should be noticed.
    2.It's easier to deal with the highest bit
    when adding,I think.
*/
#include <stdio.h>
#include <string.h>
#include <memory.h>
int main()
{
    char srca[1000], srcb[1000];
    int  dsta[1000], dstb[1000], sum[1000];
    int carry = 0;
    while (1)
    {
        memset(dsta, 0x00, sizeof(dsta));
        memset(dstb, 0x00, sizeof(dstb));
        memset(sum , 0x00, sizeof(sum));
        //test if the highest bit has a carry
        //to know the length of "sum" array to be displayed.
        carry = 0;
        //Don't forget test EOF, or I will get
        //time limit exceed.
        if (scanf("%s", srca) == EOF)
        {
            break;
        }
        getchar();
        scanf("%s", srcb);
        getchar();
        int i, j = 999;
        int longer = strlen(srca) > strlen(srcb) ? strlen(srca) : strlen(srcb);
        for (i = strlen(srca)-1; i >= 0; i--)
        {
            dsta[j--] = srca[i] - '0';
        }
        j = 999;
        for (i = strlen(srcb)-1; i >= 0; i--)
        {
            dstb[j--] = srcb[i] - '0';
        }
        for (i = 999; i >= 1; i--)
        {
            sum[i] += dsta[i] + dstb[i];
            if (sum[i] >= 10)
            {
                sum[i]   = sum[i] - 10;
                sum[i-1] += 1;
                if (i == 1000 - longer)
                {
                    carry = 1;
                }
            }
        }
        sum[0] += dsta[0] + dstb[0];
        if (sum[0] >= 10)
        {
            sum[0] = sum[0] - 10;
        }
        if (carry == 1)
            longer++;
        for (i = 1000 - longer; i <1000; i++)
        {
            printf("%d", sum[i]);
        }
        printf("\n");
    }
    return 0;
}