Completed Competitive Coding-1

Problem1.java

@@ -1 +1,37 @@
+class Problem1{
+    public static void main(String[] args){
+        Problem1 problem1 = new Problem1();
+        int[] arr = {1,2,3,4,6,7,8};
+        System.out.println("Missing element is: " + problem1.findMissingElement(arr));
+    }
+    private int findMissingElement(int[] nums){
+        if(nums == null || nums.length == 0){
+            return -1;
+        }
+        /*Logic: Perform binary search and match the current value with index.
+        * If index and value don't match search left else search right. */
+        int low = 0; int mid; int high = nums.length - 1;
 
+    //        Edge cases resolution
+        if(nums[low] != 1) return 1;
+        else if (nums.length > 1 && nums[high] != high + 1 && nums[high - 1] == high){
+            return nums.length; // Could also return high + 1
+        }
+//        Begin binary search
+        while(low <= high) {
+            mid = low + (high - low) / 2;
+//            Missing element found
+            if(nums[mid] > (mid + 1) && nums[mid - 1] == mid){
+                return mid + 1;
+            }
+            else if(nums[mid] == mid + 1){
+//                Consistent till now so search right
+                low = mid + 1;
+            }
+//            Search left
+            else high = mid - 1;
+        }
+//        If there is no missing element
+        return -1;
+    }
+}