1 #include<stdio.h>
2 #include<string.h>
3
4 void reverse( char *s ) /*将字符串逆置*/
5 {
6 int length;
7 int i = 0;
8 char temp;
9 length = strlen( s );
10 while( i < length - i - 1 )
11 {
12 temp = s[i];
13 s[i] = s[length - i - 1];
14 s[length - i - 1] = temp;
15 i++;
16 }
17 }
18
19 void AddBigNum( char* s1, char* s2, char* result )
20 {
21 int len1 = strlen( s1 );
22 int len2 = strlen( s2 );
23 int acc = 0, temp, i; /*acc为进位标记*/
24 if( s1 == NULL || s2 == NULL || result == NULL )
25 {
26 return;
27 }
28 reverse( s1 );
29 reverse( s2 );
30 for( i = 0; i < len1 && i < len2; i++ )
31 {
32 temp = s1[i] - '0' + s2[i] - '0' + acc; /*计算每位的实际和*/
33 result[i] = temp % 10 + '0'; /*通过求余数来确定每位的最终值*/
34 if( temp >= 10 ) /*通过这个if..else..条件来判断是否有进位，并设置进位值*/
35 acc = 1;
36 else
37 acc = 0;
38 }
39 if( i < len1 ) /*两个加数位数不同*/
40 {
41 for( ; i < len1; i++ )
42 {
43 temp = s1[i] - '0' + acc; /*依旧要考虑进位，比如9999 + 1的情况*/
44 result[i] = temp % 10 + '0';
45 if( temp >= 10 )
46 acc = 1;
47 else
48 acc = 0;
49 }
50 }
51 if( i < len2 )
52 {
53 for( ; i < len2; i++ )
54 {
55 temp = s2[i] - '0' + acc;
56 result[i] = temp % 10 + '0';
57 if( temp >= 10 )
58 acc = 1;
59 else
60 acc = 0;
61 }
62 }
63
64 if( acc == 1 ) /*考虑如:123 + 911 = 1034的情况，如果不增加这个条件会得到结果为034，进位被舍弃*/
65
66 result[i++] = '1';
67
68 result[i] = '\0';
69 reverse( result );
70 }
71
72 main()
73 {
74 char s1[100];
75 char s2[100];
76 char result[100];
77 while((scanf("%s %s",&s1,&s2))!=EOF)
78 {
79 AddBigNum( s1, s2, result );
80 printf( "%s\n", result );
81 }
82 }
