In this example, we’ll find missing number from Integer array but this method works only with a set of integers that are sorted and are in sequence like below:
This is a common question asked in Java Interviews.
Input:
int[] arr1 = { 1, 2, 3, 5, 6, 7 };
Output:
4
1. Java
public class FindMissingNumberFromIntegerArray {
public static void main(String[] args) {
FindMissingNumberFromIntegerArray obj = new FindMissingNumberFromIntegerArray();
int arr[] = { 1, 2, 3, 4, 6, 7, 9, 8, 10, 11, 12, 13, 14, 15 };
System.out.println(obj.findMissing(arr, 15));
}
public int findMissing(int[] arr, int num) {
int expectedSum = num * (num + 1) / 2;
int actualSum = 0;
for (int i = 0; i < arr.length; i++) {
actualSum += arr[i];
}
return expectedSum - actualSum;
}
}
Output:
5
Complete Java Solutions can be found here: Github Link