View difference between Paste ID: BdbYE9uL and G55J7pjV

-public static String add(String bits1, String bits2){
+public static String add(String bits1, String bits2) {
-        bits1 = new StringBuilder(bits1).reverse().toString();
+	int len1 = bits1.length();
-        bits2 = new StringBuilder(bits2).reverse().toString();
+	int len2 = bits2.length();
-
+	int max = Math.max(len1, len2);
-        StringBuilder result = new StringBuilder();
+	StringBuilder result = new StringBuilder(1 + max);
-
+	boolean one = false;
-        char q = '0';//for cases like: (1+1+0)=0 and 1, this (1) is stored in 1
+	for (int i = 1; i <= max; i++) {
-        for(int i = 0;i < bits1.length();i++){
+		final char c1 = len1 - i >= 0 ? bits1.charAt(len1 - i) : '0';
-            char bit1 = bits1.charAt(i);
+		final char c2 = len2 - i >= 0 ? bits2.charAt(len2 - i) : '0';
-            char bit2 = bits2.charAt(i);
+		if (('0' ^ c1) > 1 || ('0' ^ c2) > 1)
-            if(bit1 == '0'){
+			throw new IllegalArgumentException(bits1 + " + " + bits2);
-                if(bit2 == '0'){
+		if (c1 + c2 == 2 * '0') {
-                    if(q == '0'){//(0+0+0)=0 and 0
+			result.append(one ? '1' : '0');
-                        result.append('0');
+			one = false;
-                        q = '0';
+		} else if (c1 + c2 == '0' + '1') {
-                    }else if(q == '1'){//(0+0+1)=1 and 0
+			result.append(one ? '0' : '1');
-                        result.append('1');
+		} else if (c1 + c2 == 2 * '1') {
-                        q = '0';
+			result.append(one ? '1' : '0');
-                    }
+			one = true;
-                }else if(bit2 == '1'){
+		} else
-                    if(q == '0'){//(0+1+0)=1 and 0
+			throw new IllegalArgumentException(bits1 + " + " + bits2);
-                        result.append('1');
+	}
-                        q = '0';
+	if (one)
-                    }else if(q == '1'){//(0+1+1)=0 and 1
+		result.append('1');
-                        result.append('0');
+	return result.reverse().toString();
-                        q = '1';
+}