仅使用Entity Framework LINQ优化查找最小值/最大值

Question

The way I normally find the Min/Max in the database is using

var employeeWithMinSalary = employees.OrderBy(x=>x.Salary).First()
var employeeWithMaxSalary = employees.OrderByDescending(x=>x.Salary).First()

However, the performance is O(n * Log(n)).

Is there any other way to Optimize the performance to O(n) using Linq only? (No other libraries)

Answer 1

It's not necessary to sort a list to find the Min/Max value from a list. The best sorting algorithm has an average complexity of O(N*logN). Both Max and Min operations shouldn't take more than O(N), even though the list is unsorted.

You can implement the solution posted here or implementing the following code:

   private static Employee MaxBySalary(List<Employee> employees)
    {
        Employee employee = null;
        employees.ForEach(x => employee = ( employee != null && employee.Salary > x.Salary) ? employee : x );
        return employee;
    }

    private static Employee MinBySalary(List<Employee> employees)
    {
        Employee employee = null;
        employees.ForEach(x => employee = (employee != null && employee.Salary < x.Salary) ? employee : x);
        return employee;
    }

Both approaches have O(N) complexity