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Nov 18, 2025
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Add solution for Challenge 3 by yz4230 #743

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73 changes: 73 additions & 0 deletions challenge-3/submissions/yz4230/solution-template.go
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Original file line number Diff line number Diff line change
@@ -0,0 +1,73 @@
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) {
idx := -1
for i, e := range m.Employees {
if e.ID == id {
idx = i
break
}
}
if idx == -1 {
return
}
next := make([]Employee, 0, len(m.Employees)-1)
next = append(next, m.Employees[:idx]...)
next = append(next, m.Employees[idx+1:]...)
m.Employees = next
}

// GetAverageSalary calculates the average salary of all employees.
func (m *Manager) GetAverageSalary() float64 {
if len(m.Employees) == 0 {
return 0.0
}
sum := 0.0
for _, e := range m.Employees {
sum += e.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
}
Comment on lines +51 to +59
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@coderabbitai coderabbitai bot Nov 16, 2025

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⚠️ Potential issue | 🟠 Major

Returning pointer to slice element creates potential dangling pointer issue.

Returning a pointer to a slice element (&m.Employees[i]) is risky because:

  • If the slice is later modified (e.g., via RemoveEmployee or if AddEmployee triggers reallocation), the returned pointer may become invalid or point to incorrect data.
  • This is a common Go pitfall that can lead to subtle, hard-to-debug issues.

Consider returning by value or making a copy instead.

Apply this diff to return by value with a found indicator:

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

Then update the caller 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)
 	}

Committable suggestion skipped: line range outside the PR's diff.

🤖 Prompt for AI Agents 
In challenge-3/submissions/yz4230/solution-template.go around lines 51 to 59,
the function currently returns a pointer to a slice element which can become
invalid if the slice is modified; change the function to return the Employee by
value plus a boolean found flag (e.g., (Employee, bool)), iterate to find the
match and return a copy of the employee and true, and return the zero-value
Employee and false when not found; then update all call sites (e.g., in main) to
handle the two-value return, check the boolean before using the Employee, and
avoid storing or relying on pointers to slice elements.


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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