LeetCode 67. Add Binary

public class Solution { public String addBinary(String a, String b) { StringBuilder sb = new StringBuilder(); char c = '0'; int la = a.length() - 1; int lb = b.length() - 1; while (la != -1 || lb != -1) { char thisa = la != -1 ? a.charAt(la--) : '0'; char thisb = lb != -1 ? b.charAt(lb--) : '0'; sb.append((char)(thisa ^ thisb ^ c)); if (thisa != thisb && c == '1') c = '1'; else if (thisa == thisb && thisa == '1') c = '1'; else c = '0'; } if (c == '1') sb.append(c); return sb.reverse().toString(); } }