Completed Competitive-Coding-1

Problem1.java

@@ -1 +1,31 @@
+// Time Complexity : O(logn)
+// Space Complexity : O(1)
 
+// Perform binary search to check if a number is in the correct index
+// A number is in the correct index if the number = index + 1
+// If correct move to right side of array else move to left side of array
+
+class Solution {
+	public int findMissingNumber(int[] arr) {
+		int n = arr.length;
+		int low = 0;
+		int high = n-1;
+		while(low <= high) {
+			int mid = low + (high - low) / 2;
+			if(arr[mid] == mid+1) {
+				low = mid + 1;
+			}
+			else {
+				high = mid - 1;
+			}
+		}
+		return arr[low]-1;
+	}
+
+	public static void main(String args[]) {
+		Solution obj = new Solution();
+		int[] arr = new int[]{1, 2, 3, 5, 6};
+		int missingNumber = obj.findMissingNumber(arr);
+		System.out.println("The missing number is: " + missingNumber);
+	}
+}