How to Answer: What method do you use to find the missing number in an integer array of 1 to 100?
Advice and answer examples written specifically for a Software Developer job interview.
30. What method do you use to find the missing number in an integer array of 1 to 100?
How to Answer
When it comes to interview questions about finding missing numbers in an integer, that tells me that the interviewer has a specific type of role in mind for a candidate. More than likely, they are looking for an analytical thinker who can solve problems relatively easily. Let me demonstrate. Let's say I have an array number from 1 to 100. These are just random numbers for now. In a sorted array, you can compare whether a number is equal to the expected next number or not. Alternatively, you can also use the BitSet method in Java to solve this problem as well. A BitSet solution is more general, as you can use it to find more than one missing value on an integer array. Take your time to think about how you will respond to these types of questions because the interviewer is testing your ability to process and come up with an answer.
Written by Tom Dushaj on August 31st, 2021
1st Answer Example
"Having many tools at my disposal, I find that a Java solution is the best way to solve this problem. I would typically write a program to find the missing number in an array in Java, C#, or another language. The method I use is to find missing elements in an area of 100 integers, which contains numbers between 1 and 100. Looking at this problem from a high level, this can easily be solved by calculating the sum of the series using n(n+1)/2 to solve this problem. It's a quick and efficient way to do it, but keep in mind that it cannot be used if the array contains more than one number or if the array contains duplicates. Some of these solutions might require you to calculate the sum of numbers and then subtract that from the actual sum to arrive at the correct answer."
Written by Tom Dushaj on August 31st, 2021
2nd Answer Example
"I always look at different ways to solve a problem or find a solution. A step-by-step process is a simple solution that I use to find a missing number in an integer array. Let me demonstrate:
Step 1: Create an array with a number like 10001 with all zeros
Step 2: Decrease the value corresponding to the input value (A). An example would be if we have a value of 200, we will decrease that value.
Step 3: Read list (B) value and increase that value. At this point, the elements of list A would be lost, resulting in the array having performed this operating will then be positive.
Step 4: Print all the indexes of the array with a value greater than the number 0."
Written by Tom Dushaj on August 31st, 2021