[C language brush leetcode] 67. binary sum (E)

【

Here are two binary strings , Returns the sum of them （ In binary ）.

Input is Non empty String and contains only numbers  1  and  0.

Example  1:

Input : a = "11", b = "1"
Output : "100"
Example  2:

Input : a = "1010", b = "1011"
Output : "10101"
 

Tips ：

Each string consists only of characters '0' or '1' form .
1 <= a.length, b.length <= 10^4
If the string is not "0" , No leading zeros .

source ： Power button （LeetCode）
link ：https://leetcode.cn/problems/add-binary
Copyright belongs to the network . For commercial reprint, please contact the official authority , Non-commercial reprint please indicate the source .

】

A simple question , Unexpectedly, the code was written for a while , It's so delicious

1.  Apply for a character array instead of int Array

2.  Before operation -'0', Required after operation +'0'

3.  When a[i]+b[i] This needs to be reduced twice '0'

4.  Length of application  len + 2, Remember to initialize

5.  Reverse operation needs to be memorized , Instead of thinking for a while before writing

char * addBinary(char * a, char * b){
    int lena = strlen(a);
    int lenb = strlen(b);
    int i, j;
    int idx = 0;
    int len = fmax(lena, lenb);
    char *retarr = malloc(sizeof(char) *(len + 2));
    int idxtmp = 0;
    int flag = 0;

    memset(retarr, 0, sizeof(char) *(len + 2));

    i = lena - 1;
    j = lenb - 1;

    while (i >= 0 || j >= 0) {
        if (i >= 0 && j < 0) {
            idxtmp = a[i] - '0';
            i--;
        } else if (i < 0 && j >= 0) {
            idxtmp = b[j] - '0';
            j--;
        } else if (i >= 0 && j >= 0){
            idxtmp = a[i] + b[j] - '0' -'0';
            i--;
            j--;
        }

        idxtmp = idxtmp + flag;
        flag = idxtmp / 2;
        retarr[idx++] = idxtmp % 2 + '0';

    }

    if (flag != 0) {
        retarr[idx++] = flag + '0';
    }

    i = 0; //  The reverse 
    j = idx - 1;
    while (i < j) {
        char tmp = retarr[i];
        retarr[i] = retarr[j];
        retarr[j] = tmp;
        i++;
        j--;
    }

    return retarr;
}

/*
 A simple question , Unexpectedly, the code was written for a while , food 
1.  Apply for a character array instead of int Array 
2.  Before operation -'0', Required after operation +'0'
3.  When a[i]+b[i] This needs to be reduced twice '0'
4.  Length of application  len + 2, Remember to initialize 
5.  Reverse operation needs to be memorized , Instead of thinking for a while before writing 
*/