Problem Description
You are preparing for a coding test for hiring new employees. The coding test problem is
centered around the theme of ‘I Don’t Want to Be a Liar’. In this problem, you need to determine
if someone is lying based on the stories of several employees. You must develop an algorithm to
clearly distinguish who is telling the truth and who is lying in the workplace.
Problem Content
There are N employees. Each employee (A, B, C, …) claims about another employee, stating
things like ‘A is a liar’ or ‘B is a liar’. The claims of each employee are all trustworthy, and
if a claim is incorrect, it generally becomes a lie.
Input
- The first line contains the number of employees N (1 ≤ N ≤ 1000).
- The following N lines provide information about each employee’s claims. Each claim is in the format “This employee is a liar”.
Output
Output the number of the employee who has lied the most. If there is only one employee who did not lie,
output 0.
Problem Solving Process
To solve this problem, you need to analyze the relationships between employees and calculate
the number of employees who are lying based on the claims of each employee. Here, we need to
understand how each employee’s claims are connected.
Step 1: Data Structure Design
First, we need to choose a data structure that can store each employee’s claims. We can use a
Map where the employee’s number is the key and the value is a list of the employees they claim are liars.
For example, if employee 1 claims that employee 2 is a liar, the Map would look like this:
{
1: [2],
2: [3, 4],
3: [1],
...
}
Step 2: Graph Traversal (DFS or BFS)
Once the Map structure is ready, we need to determine who is telling the truth and who is
lying through graph traversal. We can use DFS (Depth-First Search) or
BFS (Breadth-First Search) algorithms for this purpose.
Step 3: Calculate Results Based on Collected Data
After the traversal is complete, calculate who has lied the most based on the information
about whether each employee is lying.
Step 4: Write Overall Code
We will implement the above steps in code using Java. Below is an example code to solve
the problem:
import java.util.*;
public class Main {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int n = scanner.nextInt();
Map> statements = new HashMap<>();
// Inputting employee claims
for (int i = 1; i <= n; i++) {
int liarIndex = scanner.nextInt();
if (!statements.containsKey(i)) {
statements.put(i, new ArrayList<>());
}
statements.get(i).add(liarIndex);
}
int maxLiars = 0;
// Calculate the number of liars for each employee
for (int i = 1; i <= n; i++) {
HashSet visited = new HashSet<>();
boolean[] isLiar = new boolean[n + 1];
isLiar[i] = true;
dfs(i, statements, visited, isLiar);
int countLiars = 0;
for (int j = 1; j <= n; j++) {
if (isLiar[j]) countLiars++;
}
maxLiars = Math.max(maxLiars, countLiars);
}
System.out.println(maxLiars);
}
private static void dfs(int employee, Map> statements,
HashSet visited, boolean[] isLiar) {
if (visited.contains(employee)) return;
visited.add(employee);
if (statements.containsKey(employee)) {
for (int liar : statements.get(employee)) {
isLiar[liar] = true;
dfs(liar, statements, visited, isLiar);
}
}
}
}
Conclusion
In this body, we defined the problem centered around ‘I Don’t Want to Be a Liar’
and explained the algorithm to solve that problem step by step.
By analyzing the information about the claims of employees, we can determine who has lied,
and through those results, we can identify the employee who has lied the most.
This process can help improve your preparation for coding tests and your problem-solving skills in algorithms.