1. Student's Major

A university maintains data on students and their majors in three tables: STUDENTS, MAJORS, and REGISTER. The university needs a list of STUDENT_NAME and MAJOR_NAME. Sort the list by STUDENT_ID and return the first 20 records.

Table Schema

STUDENTS

Name	Type	Description
STUDENT_ID	Integer	The ID of a student. This is the primary key.
STUDENT_NAME	String	The name of the student.
STUDENT_AGE	Integer	The age of the student.

MAJORS

Name	Type	Description
MAJOR_ID	Integer	The ID of a major. This is the primary key.
MAJOR_NAME	String	The name of a major.

REGISTER

Name	Type	Description
STUDENT_ID	Integer	The ID of a student. This is a foreign key.
MAJOR_ID	Integer	The ID of a major. This is a foreign key.

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2. Java: Braces

Given a list of strings of bracket characters {}, determine if the string of brackets is balanced under the following conditions:

1. It is the empty string.
2. If strings a and b are balanced, then ab is balanced.
3. If string a is balanced, then {a} is balanced.

Write a class that determines whether the brackets in each string are balanced and returns true if the string is balanced.

Example 0
s = ["{}", "{}", "{{}}"]

• s[0] exhibits condition 2 above. {} and {} are balanced, so "{}{}" is balanced. Return true.
• s[1] exhibits condition 3 above. {} is balanced, so "{{}}" is balanced. Return true.
• s[2] exhibits condition 3 above. {} is balanced, so "{{}}" is balanced. Return true.

Example 1
s = ["{", "{}}", "{{"]

• s[0] = "{" is an unbalanced string due to the open {. Return false.
• s[1] = "{}}" is an unbalanced string due to } before { has been closed. Return false.
• s[2] = "{{" is an unbalanced string because neither } is closed. Return false.

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3. Street Play in HackerLand

The Film and Theater Society of HackerLand is conducting a street play next month. The stage is n meters long, and there are m lights above it. Each light is either red, blue, or green. When all three colors shine on some area, that area appears to have white light.

Each light illuminates a range of the stage and is represented as three attributes:
color, left, right.

• Color is 1, 2, or 3 to represent red, blue, and green.
• Left and right represent the illuminated range’s extent.

Find the total number of integer positions on the stage illuminated with white light.

Example
The stage is n = 5 meters long and has m = 3 lights above it.

lights = [[1, 1, 5], [2, 2, 5], [3, 3, 5]]

• Light 1 is red and covers a range from 1 to 5.
• Light 2 is blue and covers a range from 2 to 5.
• Light 3 is green and covers a range from 3 to 5.

The range [3, 5], locations 3, 4, and 5, receive white light. Return 3.

Function Description
Complete the function getWhiteLightLength in the editor below.

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