大数加法

 1 #include <stdio.h>
 2 #include <string.h>
 3 #define N 1005
 4 int main ()
 5 {
 6     char ch2[N], ch1[N], a;
 7     int t, i, l1, j, l2, l, flag;
 8     scanf("%d", &t);
 9     while(t--)
10     {
11         flag = 0;
12         char ch[N]={0};
13         scanf(" %s", ch1);    //读入两个大数；
14         scanf(" %s", ch2);
15         l1 = strlen(ch1);    //求长度用来倒序
16         l2 = strlen(ch2);
17         for (i = 0; i<l1/2; i++)
18         {
19             a = ch1[i];
20             ch1[i] = ch1[l1-i-1];  //l1-i-1是因为最后一个数据存在l-1中
21             ch1[l1-i-1] = a;
22         }
23         for (i = 0; i<l2/2; i++)
24         {
25             a = ch2[i];
26             ch2[i] = ch2[l2-i-1];
27             ch2[l2-i-1] = a;
28         }
29         if(ch1[0]+ch2[i]-‘0‘-‘0‘>9)      //判断第一位是否进位
30             flag = 1;
31         for (i = 0, j=0; i<l1&&j<l2;i++, j++)
32         {
33             ch[i] += ch1[i]-‘0‘+ch2[j]-‘0‘+‘0‘;    //ch读入的是ascll码上的值， 要进行转换；
34             if(ch[i]-‘9‘>0)
35             {
36                 ch[i]-=10;
37                 ch[i+1]++;
38             }
39         }
40 
41         if (l1>l2)
42         {
43             for(; i<l1; i++)
44                 ch[i] = ch1[i];
45         }
46         else if(l1<l2)
47         {
48             for(; i<l2; i++)
49                 ch[i] = ch2[i];
50         }
51         l = strlen(ch);
52         for (i = 0; i<l; i++)
53         {
54             a = ch[i];
55             ch[i] = ch[l-i-1];
56             ch[l-i-1] = a;
57         }
58         if(flag == 1)
59         {
60             printf("1");
61             for (i = l-2; i>=0; i--)          //若进位的话要改变长度 首位是1；
62                 printf("%d", ch[i]-‘0‘);
63         }
64         else
65             for (i = l-1; i>=0; i--)
66                 printf("%d", ch[i]-‘0‘);
67         printf("\n");
68     }
69     return 0;
70 }