11class Solution {
22 public String addBinary (String a , String b ) {
3- int al = a .length (), bl = b .length (), di = Math .max (al , bl );
4- char [] ac = a .toCharArray (), bc = b .toCharArray (), re = new char [di + 1 ];
5- boolean jw = false ;
6- for (int i = 1 ; i <= di ; i ++) {
7- int alc = al - i , blc = bl - i ;
8- char aChar = alc >= 0 ? ac [alc ] : '0' ;
9- char bChar = blc >= 0 ? bc [blc ] : '0' ;
10- if (aChar == bChar ) {
11- re [di + 1 - i ] = jw ? '1' : '0' ;
12- jw = aChar == '1' ;
13- } else re [di + 1 - i ] = jw ? '0' : '1' ;
3+ StringBuilder reverseAnswer = new StringBuilder ();
4+ int maxLength = Math .max (a .length (), b .length ());
5+ int carry = 0 ;
6+ 7+ for (int i = 0 ;i < maxLength ;i ++) {
8+ carry += i < a .length () ? a .charAt (a .length () - 1 - i ) - 48 : 0 ;
9+ carry += i < b .length () ? b .charAt (b .length () - 1 - i ) - 48 : 0 ;
10+ 11+ reverseAnswer .append (carry % 2 );
12+ carry /= 2 ;
1413 }
15- if (jw ) re [0 ] = '1' ;
16- StringBuilder builder = new StringBuilder ();
17- for (char c : re ) if (c != 0 ) builder .append (c );
18- return builder .toString ();
14+ 15+ if (carry == 1 ) {
16+ reverseAnswer .append (1 );
17+ }
18+ return reverseAnswer .reverse ().toString ();
1919 }
2020}
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