Added Merge Strings Alternately.java

Author: varunu28

Easy/Merge Strings Alternately.java

@@ -0,0 +1,19 @@
+class Solution {
+  public String mergeAlternately(String word1, String word2) {
+    int idx1 = 0;
+    int idx2 = 0;
+    StringBuilder sb = new StringBuilder();
+    boolean first = true;
+    while (idx1 < word1.length() && idx2 < word2.length()) {
+      sb.append(first ? word1.charAt(idx1++) : word2.charAt(idx2++));
+      first = !first;
+    }
+    while (idx1 < word1.length()) {
+      sb.append(word1.charAt(idx1++));
+    }
+    while (idx2 < word2.length()) {
+      sb.append(word2.charAt(idx2++));
+    }
+    return sb.toString();
+  }
+}