Merge pull request #1977 from Mahim1997/dev/67_Java

67. Add Binary

Author: tahsintunan

java/0067-Add-Binary.java

@@ -0,0 +1,41 @@
+class Solution {
+    public String addBinary(String a, String b) {
+        // Go from right to left
+        int len1 = a.length();
+        int len2 = b.length();
+
+        int minLen = Math.min(len1, len2);
+        int maxLen = Math.max(len1, len2);
+
+        int index1 = len1 - 1;
+        int index2 = len2 - 1;
+
+        StringBuilder bld = new StringBuilder();
+        boolean carry = false;
+
+        while((index1 >= 0) || (index2 >= 0) || carry) {
+            char c1 = (index1 >= 0) ? a.charAt(index1) : '0';
+            char c2 = (index2 >= 0) ? b.charAt(index2) : '0';
+
+            char sum;
+            if((c1 == '0') && (c2 == '0')) {        // Both zeros
+                sum = carry ? '1' : '0';
+                carry = false;
+            }
+            else if((c1 == '1') && (c2 == '1')) {   // Both ones
+                sum = carry ? '1' : '0';
+                carry = true;
+            }
+            else {                                  // Any one with a one
+                sum = carry ? '0' : '1';
+                // carry will be forwarded
+            }
+            bld.append(sum);
+
+            index1--;
+            index2--;
+        }
+
+        return bld.reverse().toString();
+    }
+}