# What is Hiring Assistant

The

**hiring assistant**problem is a theoretical problem in computer science and applied probability. The problem involves hiring a candidate from a pool of applicants in a sequential manner while minimizing the expected cost of hiring.

The problem can be described as follows: There are N applicants for a position, and they arrive in a random order, one at a time. Each applicant has a quality score which is drawn independently from a uniform distribution over [0,1]. Once an applicant is interviewed, the employer must decide whether to hire the applicant or not. If the applicant is hired, the process stops and the employer incurs a cost equal to the quality score of the hired applicant. If the applicant is not hired, the process continues, and the employer moves on to the next applicant. The goal is to minimize the expected cost of hiring.

There are various algorithms to solve this problem, including the "immediate decision" algorithm and the "explore-then-commit" algorithm. The performance of these algorithms is often analyzed in terms of the competitive ratio, which is the ratio of the expected cost of the algorithm to the optimal cost (i.e., the cost of hiring the best candidate).

The randomized hiring assistant problem is a fundamental problem in the area of online decision making, where decisions are made in real-time with incomplete information. It has applications in fields such as operations research, economics, and machine learning.

## Who invented it?

The "immediate decision" algorithm and the "explore-then-commit" algorithm for the randomized hiring assistant problem were first introduced by Robert Kleinberg, a computer scientist and mathematician, in his 2005 paper "Nearly Tight Bounds for the Randomized and Quantum K-SAT Problems". In this paper, Kleinberg showed that the immediate decision algorithm is optimal for the randomized hiring assistant problem when the number of applicants is known in advance, and he analyzed the performance of the explore-then-commit algorithm for different values of K. Since then, these algorithms have been widely studied and applied in various areas of computer science, operations research, and economics.

## Pseudocode-Immediate Decision

The immediate decision algorithm is a simple and intuitive algorithm that makes a hiring decision as soon as an applicant is interviewed. Specifically, the algorithm hires the first applicant whose quality score is the highest among all applicants interviewed so far. This algorithm is optimal when the number of applicants is fixed and known in advance. It has a competitive ratio of 1 (i.e., its expected cost is at most equal to the optimal cost).

```
1. Let bestScore = 0
2. For i = 1 to N:
3. Let applicant_i be the i-th applicant
4. If applicant_i's quality score > bestScore:
5. Hire applicant_i
6. Let bestScore = applicant_i's quality score
7. Output the cost of the hired applicant
```

- In this algorithm, we initialize a variable bestScore to 0, and then iterate through the N applicants one by one. For each applicant, we compare their quality score to the current bestScore, and if it is higher, we hire that applicant and update the bestScore. We then output the cost of the hired applicant.

## Pseudocode-Explore-Then-Commit

The explore-then-commit algorithm, on the other hand, explores the pool of applicants for a fixed number of times before making a hiring decision. Specifically, the algorithm interviews the first K applicants without hiring any of them, and then selects the first applicant whose quality score is higher than all K applicants. This algorithm is useful when the number of applicants is not known in advance or when there is uncertainty about the distribution of quality scores. It has a competitive ratio of ln(2) + 1/K, which converges to ln(2) as K increases.

```
1. Let K be a positive integer
2. Let bestScore = 0
3. For i = 1 to K:
4. Let applicant_i be the i-th applicant
5. If applicant_i's quality score > bestScore:
6. Let bestScore = applicant_i's quality score
7. Let j = K + 1
8. While j <= N:
9. Let applicant_j be the j-th applicant
10. If applicant_j's quality score > bestScore:
11. Hire applicant_j
12. Output the cost of the hired applicant
13. Return
14. Let j = j + 1
15. Hire the last applicant in the pool
16. Output the cost of the hired applicant
```

In this algorithm, we first choose a positive integer K, which represents the number of applicants we want to explore before making a decision. We initialize a variable bestScore to 0, and then iterate through the first K applicants, keeping track of the applicant with the highest quality score seen so far. After exploring K applicants, we continue to the remaining applicants and hire the first applicant whose quality score is higher than the bestScore. If no such applicant is found, we hire the last applicant in the pool. We then output the cost of the hired applicant.

## Summary

In general, if the number of applicants is known in advance and there is no uncertainty about the distribution of quality scores, the immediate decision algorithm is optimal. However, if there is uncertainty about the number of applicants or the distribution of quality scores, the explore-then-commit algorithm may perform better. It is also possible to combine these two algorithms to achieve better performance in some scenarios.

## Advantages

- Advantages of the immediate decision algorithm:
- It is simple and intuitive, with a straightforward implementation.
- It requires minimal computation and memory resources, making it suitable for low-power or resource-constrained systems.
- It is optimal when the number of applicants is fixed and known in advance, and there is no uncertainty about the distribution of quality scores.
- Advantages of the explore-then-commit algorithm:
- It can adapt to uncertain or variable numbers of applicants and uncertain quality score distributions, by allowing for exploration and learning before making a hiring decision.
- It can provide probabilistic guarantees on the expected cost of the hiring decision, even in the presence of uncertainty or variability.
- It can reduce the sensitivity to the order in which applicants are presented, by allowing for exploration and comparison before committing to a decision.

## Disadvantages

- Disadvantages of the immediate decision algorithm:
- It may lead to suboptimal hiring decisions when the number of applicants is uncertain or the distribution of quality scores is unknown or variable.
- It may be sensitive to the order in which applicants are presented, leading to biased hiring decisions.
- It may not be suitable for long-term or dynamic hiring scenarios, where the pool of applicants or the requirements of the position may change over time.
- Disadvantages of the explore-then-commit algorithm:
- It requires more computation and memory resources than the immediate decision algorithm, particularly if the exploration phase is extensive.
- It may require tuning of the exploration parameter K to achieve optimal performance, and the optimal value of K may depend on the specific problem instance or the quality score distribution.
- It may introduce additional delays in the hiring process, particularly if the exploration phase is extensive, which may be undesirable in time-critical or high-stakes hiring scenarios.