storing location of mismatch and checking if replacing equals other string

Author: Arjiit

Strings/buddyStrings.java

@@ -0,0 +1,35 @@
+class Solution {
+    public boolean buddyStrings(String A, String B) {
+        if (A.length() != B.length()) {
+            return false;
+        }
+        HashSet<Character> setA = new HashSet<>();
+        HashSet<Character> setB = new HashSet<>();
+        boolean dupA = false;
+        boolean dupB = false;
+        List<Integer> mismatch = new ArrayList<>();
+        for (int i=0; i<A.length(); i++) {
+            if (setA.contains(A.charAt(i))) {
+                dupA = true;
+            }
+            if (setB.contains(B.charAt(i))) {
+                dupB = true;
+            }
+            
+            if(A.charAt(i) != B.charAt(i)) {
+                mismatch.add(i);
+            }
+            setA.add(A.charAt(i));
+            setB.add(B.charAt(i)); 
+        }
+        if (mismatch.size() == 2) {
+            if ((A.charAt(mismatch.get(0)) == B.charAt(mismatch.get(1)))&& (A.charAt(mismatch.get(1)) == B.charAt(mismatch.get(0)))) {
+                return true;
+            }
+        }
+        if (dupA && dupB && A.equals(B)) {
+            return true;
+        }
+      return false;  
+    }
+}