public String addBinary(String a, String b) {

// Start typing your Java solution below

// DO NOT write main() function

StringBuffer a1 = (new StringBuffer(a).reverse());

StringBuffer b1 = (new StringBuffer(b).reverse());

int al = a1.length();

int bl = b1.length();

if(al<bl){

StringBuffer k;

k = a1;

a1 = b1;

b1 = k;

int l = al;

al = bl;

bl = l;

}

int add = 0;

StringBuffer c = new StringBuffer("");

for(int i=0;i<al;i++){

if(i>=bl || b1.charAt(i)==0){

int k = a1.charAt(i)-'0'+add ;

if(k==2){

k=0;

add = 1;

c.append(k);

}else{

add = 0;

c.append(k);

}

}

else{

int k = a1.charAt(i)+b1.charAt(i)-'0'-'0'+add;

if(k>=2){

k=k-2;

add = 1;

c.append(k);

}else{

add = 0;

c.append(k);

}

}

}

if(add==1){

c.append(1);

}

return c.reverse().toString();

}