solves contains duplicates ii

Author: anishLearnsToCode

Diff for: src/ContainsDuplicateII.java

@@ -0,0 +1,68 @@
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+
+public class ContainsDuplicateII {
+    public static void main(String[] args) {
+        System.out.println(containsNearbyDuplicate(new int[] {1, 2, 3, 1, 2, 3}, 2));
+    }
+
+//    private static class Frequency {
+//        private static final Map<Integer, Integer> frequency = new HashMap<>();
+//
+//        public static Frequency withWindowSize(int[] array, int window) {
+//            Frequency frequency = new Frequency();
+//            for (int index = 0 ; index < window ; index++) {
+//                frequency.add(array[index]);
+//            }
+//            return frequency;
+//        }
+//
+//        public void add(int element) {
+//            frequency.put(element, frequency.getOrDefault(element, 0) + 1);
+//        }
+//
+//        public void remove(int element) {
+//            if (contains(element)) {
+//                frequency.put(element, frequency.get(element) - 1);
+//            }
+//        }
+//
+//        public boolean contains(int element) {
+//            return frequency.getOrDefault(element, 0) > 0;
+//        }
+//    }
+//
+//    public static boolean containsNearbyDuplicate(int[] array, int k) {
+//        Frequency slidingWindow = Frequency.withWindowSize(array, k);
+//        for (int index = k ; index < array.length ; index++) {
+//            if (slidingWindow.contains(array[index])) {
+//                return true;
+//            }
+//            slidingWindow.add(array[index]);
+//            slidingWindow.remove(array[index - k]);
+//        }
+//        return false;
+//    }
+
+    public static boolean containsNearbyDuplicate(int[] nums, int k) {
+        Set<Integer> checkForDuplicatesSet = new HashSet<>();
+        for (int i = 0; i < nums.length; i++) {
+            int preSize = checkForDuplicatesSet.size();
+            int currentNum = nums[i];
+            checkForDuplicatesSet.add(currentNum);
+            if (checkForDuplicatesSet.size() == preSize) {
+                int dupK = k, reverse = i - 1;
+                while ( dupK > 0) {
+                    if ( nums[reverse] == currentNum) {
+                        return true;
+                    }
+                    dupK--;
+                    reverse--;
+                }
+            }
+        }
+        return false;
+    }
+}