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Merged
merged 2 commits into from
Oct 16, 2025
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Add solution for Challenge 3 by Kosench #561

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39b4582
Add solution for Challenge 3
go-interview-practice-bot[bot] Oct 11, 2025
3b4a93d
Merge branch 'RezaSi:main' into challenge-3-Kosench-1760209786
Kosench Oct 14, 2025
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67 changes: 67 additions & 0 deletions challenge-3/submissions/Kosench/solution-template.go
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Original file line number Diff line number Diff line change
@@ -0,0 +1,67 @@
package main

import "fmt"

type Employee struct {
ID int
Name string
Age int
Salary float64
}

type Manager struct {
Employees []Employee
}

// AddEmployee adds a new employee to the manager's list.
func (m *Manager) AddEmployee(e Employee) {
m.Employees = append(m.Employees, e)
}

// RemoveEmployee removes an employee by ID from the manager's list.
func (m *Manager) RemoveEmployee(id int) {
for i := range m.Employees {
if m.Employees[i].ID == id {
m.Employees = append(m.Employees[:i], m.Employees[i+1:]...)
return
}
}
}
Comment on lines +21 to +29
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⚠️ Potential issue | 🔴 Critical

Pointer invalidation risk when combining FindEmployeeByID and RemoveEmployee.

FindEmployeeByID returns a pointer to an element in the Employees slice. When RemoveEmployee modifies the slice by reslicing, any previously returned pointers can become invalid or point to different employees. This creates a critical correctness issue.

Example scenario:

emp := manager.FindEmployeeByID(1)  // returns pointer to slice element
manager.RemoveEmployee(1)            // reslices, shifting elements
// emp now may point to wrong employee or invalid memory

Apply this diff to return a copy instead of a pointer:

 // FindEmployeeByID finds and returns an employee by their ID.
-func (m *Manager) FindEmployeeByID(id int) *Employee {
+func (m *Manager) FindEmployeeByID(id int) (Employee, bool) {
 	for i := range m.Employees {
 		if m.Employees[i].ID == id {
-			return &m.Employees[i]
+			return m.Employees[i], true
 		}
 	}
-	return nil
+	return Employee{}, false
 }

And update the call site in main:

-	employee := manager.FindEmployeeByID(2)
+	employee, found := manager.FindEmployeeByID(2)
 
 	fmt.Printf("Average Salary: %f\n", averageSalary)
-	if employee != nil {
-		fmt.Printf("Employee found: %+v\n", *employee)
+	if found {
+		fmt.Printf("Employee found: %+v\n", employee)
 	}

Also applies to: 45-53

🤖 Prompt for AI Agents 
In challenge-3/submissions/Kosench/solution-template.go around lines 21-29 (and
also address similar code at lines 45-53), FindEmployeeByID currently returns a
pointer into the Employees slice which can be invalidated by RemoveEmployee's
reslicing; change FindEmployeeByID to return an Employee value and a boolean
(e.g., func (m *Manager) FindEmployeeByID(id int) (Employee, bool)) so callers
receive a copy, update all call sites (including main) to handle the (Employee,
bool) return (check the bool before using the returned value), and keep
RemoveEmployee as-is; this prevents pointer invalidation by ensuring callers
work with copies rather than pointers into the slice.


// GetAverageSalary calculates the average salary of all employees.
func (m *Manager) GetAverageSalary() float64 {
if len(m.Employees) == 0 {
return 0
}

var sum float64
for _, employee := range m.Employees {
sum += employee.Salary
}

return sum / float64(len(m.Employees))
}

// FindEmployeeByID finds and returns an employee by their ID.
func (m *Manager) FindEmployeeByID(id int) *Employee {
for i := range m.Employees {
if m.Employees[i].ID == id {
return &m.Employees[i]
}
}
return nil
}

func main() {
manager := Manager{}
manager.AddEmployee(Employee{ID: 1, Name: "Alice", Age: 30, Salary: 70000})
manager.AddEmployee(Employee{ID: 2, Name: "Bob", Age: 25, Salary: 65000})
manager.RemoveEmployee(1)
averageSalary := manager.GetAverageSalary()
employee := manager.FindEmployeeByID(2)

fmt.Printf("Average Salary: %f\n", averageSalary)
if employee != nil {
fmt.Printf("Employee found: %+v\n", *employee)
}
}
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