Given two binary strings, return their sum (also a binary string).
For example,
a = "11"
b = "1"
Return "100".
题目：求2个二进制字符串的和，结果也要二进制字符串输出。
1 char* addBinary(char* a, char* b) {
2 int i = strlen(a)-1;
3 int j = strlen(b)-1;
4 int c = 0;
5 char temp;
6 char *p = (char*)malloc(i > j ? i+3 :j+3); //分配字符串空间
7 char *s = p;
8 while(i >= 0 || j >= 0 || c == 1)
9 {
10 c += i >= 0 ? a[i--] - 48 : 0; //字符串每一位相加
11 c += j >= 0 ? b[j--] - 48 : 0;
12 *s++ = c % 2 + 48;
13 c = c/2; //根据c的值每次要进位
14 }
15 *s = '\0';
16 i = 0;
17 j = strlen(p)-1;
18 while(i < j) //反转字符串
19 {
20 temp = p[j];
21 p[j] = p[i];
22 p[i] = temp;
23 i++;
24 j--;
25 }
26 return p;
27 }