大数加法

void B_add(char *a, char *b, int i, int r)  // a = a + b, i为第i位，r为进位
{
    int d = r;
    if(i >= strlen(b))  //以b终结为return的标识
    {
        if(r == 0)
        {
            if(!(a[i] >= '0' && a[i] <= '9')) a[i] = '\0';
            return;
        }
    }
    else d += b[i] - '0';
    if(i < strlen(a)) d += a[i] - '0';
    a[i] = d % 10 + '0';    //  赋给a时别忘了 + '0'
    B_add(a, b, i + 1, d / 10);
}

 

循环写法：

void add(char *a, char *b)
{
    int i = 0, r = 0, d;
    int len1 = strlen(a), len2 = strlen(b);
    while(i <= len1 || i <= len2)
    {
        d = r;
        if(i < len1) d += a[i] - '0';
        if(i < len2) d += b[i] - '0';
        a[i] = '0' + d % 10;
        r = d / 10;
        i++;
    }
    if(d == 0) a[i - 1] = '\0';
    else a[i] = '\0';

}

 

 

6.2.(3)

#include <stdio.h>
#include <string.h>
#define maxn 10010

void add(char *str, char *tmp)
{
    int d, r, len1, len2, i;
    i = r = 0;
    len1 = strlen(str);
    len2 = strlen(tmp);
    while(i < len1 || i < len2)
    {
        d = 0;
        if(i < len1) d += str[i] - '0';
        if(i < len2) d += tmp[i] - '0';
        d += r;
        str[i] = '0' + d % 10;
        r = d / 10;
        i++;
    }
    if(r != 0) str[i] = '0' + r, str[i + 1] = '\0';
    else str[i] = '\0';

}

void print(char *str)
{
    int i;
    int len = strlen(str);
    for(i = len - 1; i >= 0; i--)
        printf("%c", str[i]);
    printf("\n");

}



int main()
{
    int a, n, cnt, i, r, d;
    int len1, len2;
    char str[maxn], tmp[maxn];
    str[0] = '0', str[1] = '\0';
    scanf("%d%d", &a, &n);
    cnt = r = 0;
    while(n--)
    {
        tmp[cnt] = '0' + a;
        tmp[cnt + 1] = '\0';
        add(str, tmp);
        print(str);
        cnt++;
    }

    return 0;
}