Mock1 Completed

FindMissingInSortedArray.java

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+
+// TC: O(logn)
+// SC: O(1)
+// Approach:
+/*
+ * Brute Force: Linear search if index != nums[index+1] then return that number is missing so return index+1
+ * Optimized: Binary Search 
+ * if (mid + 1 == arr[mid]) that means all the elements from start to mid are present so start = mid + 1 else end = mid - 1
+ */
+
+class Solution {
+    int missingNumber(int arr[]) {
+        // code here
+        int start = 0;
+        int end = arr.length - 1;
+
+        while(start <= end){
+            //int overflow
+            int mid = start + (end - start) / 2;
+
+            if(mid + 1 == arr[mid]){
+                start = mid + 1;
+            }
+            else
+                end = mid - 1;
+        }
+        return start + 1;
+    }
+}