67. 二进制求和c

int max(int i,int j){
    if(i>j) return i;
    return j;
}

void reverse(char* s,int head,int tail){
    while(head<=tail){
        char c=s[head];
        s[head]=s[tail];
        s[tail]=c;
        head++;
        tail--;
    }
}

char* addBinary(char* a, char* b) {
    int na=strlen(a),nb=strlen(b);
    int n=max(na,nb);
    reverse(a,0,na-1);
    reverse(b,0,nb-1);
    char* array=(char*)malloc(sizeof(char)*(n+4));
    int pre=0,index=0;
    while(index<n){
        int x=0;
        int y=0;
        if(index<na) x=a[index]-'0';
        if(index<nb) y=b[index]-'0';
        char t=(x+y+pre)%2+'0';
        array[index++]=t;
        pre=(x+y+pre)/2;
    }
    if(pre==1) array[index++]='1';
    array[index]=0;
    reverse(array,0,index-1);
    return array;
}