https://m.blog.naver.com/eviltwin/221286003266

Consecutive Numbers

 문제 설명

Create table If Not Exists Employee (id int, name varchar(255), salary int, departmentId int)
Create table If Not Exists Department (id int, name varchar(255))
Truncate table Employee
insert into Employee (id, name, salary, departmentId) values ('1', 'Joe', '70000', '1')
insert into Employee (id, name, salary, departmentId) values ('2', 'Jim', '90000', '1')
insert into Employee (id, name, salary, departmentId) values ('3', 'Henry', '80000', '2')
insert into Employee (id, name, salary, departmentId) values ('4', 'Sam', '60000', '2')
insert into Employee (id, name, salary, departmentId) values ('5', 'Max', '90000', '1')
Truncate table Department
insert into Department (id, name) values ('1', 'IT')
insert into Department (id, name) values ('2', 'Sales')

+--------------+---------+
| Column Name  | Type    |
+--------------+---------+
| id           | int     |
| name         | varchar |
| salary       | int     |
| departmentId | int     |
+--------------+---------+
id is the primary key column for this table.
departmentId is a foreign key of the ID from the Department table.
Each row of this table indicates the ID, name, and salary of an employee. It also contains the ID of their department.

+-------------+---------+
| Column Name | Type    |
+-------------+---------+
| id          | int     |
| name        | varchar |
+-------------+---------+
id is the primary key column for this table.
Each row of this table indicates the ID of a department and its name.

 입출력 예

Example 1:

Input: 
Employee table:
+----+-------+--------+--------------+
| id | name  | salary | departmentId |
+----+-------+--------+--------------+
| 1  | Joe   | 70000  | 1            |
| 2  | Jim   | 90000  | 1            |
| 3  | Henry | 80000  | 2            |
| 4  | Sam   | 60000  | 2            |
| 5  | Max   | 90000  | 1            |
+----+-------+--------+--------------+
Department table:
+----+-------+
| id | name  |
+----+-------+
| 1  | IT    |
| 2  | Sales |
+----+-------+
Output: 
+------------+----------+--------+
| Department | Employee | Salary |
+------------+----------+--------+
| IT         | Jim      | 90000  |
| Sales      | Henry    | 80000  |
| IT         | Max      | 90000  |
+------------+----------+--------+

Explanation: Max and Jim both have the highest salary in the IT department and Henry has the highest salary in the Sales department.

 Oracle Query

select
D.Name as Department, E.Name as Employee, Salary
from Employee E inner join Department D
on E.DepartmentID = D.ID
where Salary = (select max(Salary)
                from Employee
                where E.DepartmentID = DepartmentID);

* 참고 링크 : https://leetcode.com/problems/department-highest-salary/discuss/1064441/Most-Efficient-Oracle-solution

 출처

https://leetcode.com/problems/department-highest-salary/

Prime Number of Set Bits in Binary Representation

 문제 설명

Given two integers left and right, return the count of numbers in the inclusive range [left, right] having a prime number of set bits in their binary representation.

Recall that the number of set bits an integer has is the number of 1's present when written in binary.

• For example, 21 written in binary is 10101, which has 3 set bits.

왼쪽과 오른쪽 두 개의 정수가 주어지면 이진 표현에 소수의 세트 비트를 갖는 포함 범위[좌, 우]의 숫자 카운트를 반환합니다.

정수가 갖는 세트 비트의 수는 이진수로 쓸 때 존재하는 1의 수라는 것을 기억하라.

예를 들어, 이진법으로 작성된 21은 10101이고, 3개의 세트 비트를 가지고 있다.

 제한 사항

• 1 <= left <= right <= 106
• 0 <= right - left <= 104

 입출력 예

Example 1:

Input: left = 6, right = 10
Output: 4
Explanation:
6  -> 110 (2 set bits, 2 is prime)
7  -> 111 (3 set bits, 3 is prime)
8  -> 1000 (1 set bit, 1 is not prime)
9  -> 1001 (2 set bits, 2 is prime)
10 -> 1010 (2 set bits, 2 is prime)
4 numbers have a prime number of set bits.

Example 2:

Input: left = 10, right = 15
Output: 5
Explanation:
10 -> 1010 (2 set bits, 2 is prime)
11 -> 1011 (3 set bits, 3 is prime)
12 -> 1100 (2 set bits, 2 is prime)
13 -> 1101 (3 set bits, 3 is prime)
14 -> 1110 (3 set bits, 3 is prime)
15 -> 1111 (4 set bits, 4 is not prime)
5 numbers have a prime number of set bits.

 Python 코드

Python code 

class Solution:
    def countPrimeSetBits(self, L: int, R: int) -> int:
        return sum(bin(i).count('1') in [2,3,5,7,11,13,17,19] for i in range(L, R+1))

bin(i).count('1') # 이진 표현에서 1의 수가 소수인 경우

bin(i).count('1') in [2, 3, 4, 5, 7, 11, 13, 17, 19]  

# 이진 표현에서 1의 수가 [2, 3, 4, 5, 7, 11, 13, 17, 19]에 빈도가 있는 경우

sum(bin(i).count('1') in [2, 3, 5, 7, 11, 13, 17, 19] for i in range(L, R+1))

# sum( ) 함수를 이용하여 count를 증가시킨다.

* 참고 링크 1 : https://leetcode.com/problems/prime-number-of-set-bits-in-binary-representation/discuss/801535/Python-3-One-Line

 C++ 코드

C ++ code

// c++ code
#include <cmath>
class Solution {
public:
    int countPrimeSetBits(int L, int R) {
        int res = 0;
        for (int num = L; num <= R; num++) {
            int count = countOne(num);
            if (isPrime(count))
                res++;
        }
        return res;
    }
    
    bool isPrime(int num) {
        if (num <= 3)
            return num > 1;
        
        int square_root = sqrt(num);
        for (int i = 2; i <= square_root; i++) {
            if (num % i == 0)
                return false;
        }
        return true;
    }
    
    int countOne(int num) {
        vector<int> bin = dec2bin(num);
        int count = 0;
        for (auto i = bin.begin(); i < bin.end(); i++) {
            if (*i == 1)
                count++;
        }
        return count;
    }
    
    vector<int> dec2bin(int num) {
        vector<int> bin;
        while (num != 0) {
            bin.push_back(num % 2);
            num /= 2;
        }
        reverse(bin.begin(), bin.end());
        return bin;
    }
};

* 참고 링크 : https://leetcode.com/problems/prime-number-of-set-bits-in-binary-representation/discuss/376499/C%2B%2B-and-Python-3-bad-performance-need-to-improve

 출처

https://leetcode.com/problems/prime-number-of-set-bits-in-binary-representation/

Power of Four

 문제 설명

Given an integer n, return true if it is a power of four. Otherwise, return false.

An integer n is a power of four, if there exists an integer x such that n == 4x.

 제한 사항

• -231 <= n <= 231 - 1

 입출력 예

Example 1:

Input: n = 16
Output: true

Example 2:

Input: n = 5
Output: false

Example 3:

Input: n = 1
Output: true

 Python 코드

Python code 

class Solution:
    def isPowerOfFour(self, n: int) -> bool:
        return math.log(n, 1/4) % 1 == 0 if n > 0 else False

* 참고 링크 : https://leetcode.com/problems/power-of-four/discuss/637372/Python-3-Single-line

• math.log( ) 함수 이용 // loops(반복문) 또는 recursion(재귀)를 피하는 방법 중 하나// x : 필수의 로그를 계산할 값을 지정// base : 선택적으로 사용할 로그 베이스 (Default 값 : e)
  • 참고 링크 : https://www.w3schools.com/python/ref_math_log.asp
• ( 값이 0 또는 음수이면 ValueError 반환, 값이 숫자가 아니면 TypeError를 반환)
• math.log(x, base)

 C++ 코드

C ++ code

class Solution {
public:
    bool isPowerOfFour(int num) {
        return num > 0 && (num & (num - 1)) == 0 && (num - 1) % 3 == 0;
    }
};

* 참고 링크 : https://leetcode.com/problems/power-of-four/discuss/80460/1-line-C%2B%2B-solution-without-confusing-bit-manipulations

 출처

https://leetcode.com/problems/power-of-four/

Session Tracking란?

 Session Tracking 특징

 출처

+ 강의 교재

Filter API란?

 Filter API 특징

 출처

+ 강의 교재