INC Practice for LB08

Coding practice for Algorithm Design and Analysis (COMP6049001).

How to join the contest

1. Open the contest link: https://vjudge.net/contest/858200

2. Log in to vjudge. If you do not have an account yet, register one (free) at https://vjudge.net.

3. If you are asked for a password or access code, enter:

   LA08-ADA

4. Once you are in, open the Problem tab and choose a problem (A to L).

5. Click Submit, choose the language C++ (pick C++17 if available), paste your code, and submit.

6. Check your result in the Status tab. A problem is solved when the verdict is Accepted.

If vjudge asks you to bind a Codeforces browser session

Most problems in this contest come from Codeforces. When you submit one of them, vjudge may ask you to bind your Codeforces browser session. This means vjudge needs the login cookie of your own Codeforces account (called JSESSIONID). Follow these steps:

1. Log in to Codeforces at https://codeforces.com in the same browser you use for vjudge. If you do not have a Codeforces account, register one first (free).
2. Open the browser developer tools while you are on a codeforces.com page:
   • Press F12, or Ctrl + Shift + I (Windows/Linux), or Cmd + Option + I (Mac).
3. Open the cookie list:
   • Chrome / Edge: click the Application tab (if you do not see it, click the >> arrow). Then in the left panel open Storage → Cookies → https://codeforces.com.
   • Firefox: click the Storage tab, then open Cookies → https://codeforces.com.
4. Find the cookie named JSESSIONID in the list.
5. Copy its Value. Double-click the value in the Value column and copy it (Ctrl + C). It is a long string of letters and numbers.
6. Go back to vjudge, paste the value into the box that asks for JSESSIONID, and confirm.
7. Submit your solution again.

Notes:

• If vjudge asks for another cookie as well, find it in the same list and copy its value in the same way.
• The JSESSIONID works like a password for your Codeforces login. Do not share it with anyone and do not post it in any chat or screenshot. Only paste it into vjudge.
• If you log out of Codeforces, or the session expires, the value stops working. Log in to Codeforces again and repeat the steps above.
• If you cannot find JSESSIONID, make sure you are logged in to Codeforces and that you opened the cookie list for codeforces.com, not vjudge.net.
• Problems from other sites (UVa, SPOJ, CSES) are not affected by this.

Quick tips

• Read the input from the keyboard (cin) and write the output to the screen (cout). Do not read or write files.
• Check the input limits in each problem. If the numbers are large, use long long.
• Start from problem A. The problems go from easiest to hardest, and K and L are bonus problems.
• If you get Wrong Answer, try a small input of your own and compare it with a manual calculation.
• If you get Time Limit Exceeded, your algorithm is probably too slow. Think about a faster approach.

Problem list

#	Problem	Short description	Topic
A	Watermelon	Can a watermelon of weight w be split into two positive even parts?	Basic conditions
B	Wrong Subtraction	Apply a "wrong" subtraction rule k times, then print the result.	Simulation
C	Hit the Lottery	What is the minimum number of bills (1, 5, 10, 20, 100) needed to pay n?	Greedy
D	Array Rearrangement	Can array b be rearranged so that a[i] + b[i] ≤ x for every i?	Sorting, greedy
E	Payment Without Change	With a coins of value n and b coins of value 1, can you pay exactly S?	Greedy
F	Honest Coach	Split the athletes into two teams so that the difference between max(A) and min(B) is as small as possible.	Sorting
G	Same Differences	Count pairs i < j with a[j] − a[i] = j − i.	Hash table
H	Books	How many books in a row can be read within time t, at most?	Two pointers
I	Add All	Add all numbers together; each addition costs its result. Find the minimum total cost.	Greedy, priority queue
J	Movie Festival	Choose as many movies as possible with no overlapping schedules.	Greedy
K	Largest Rectangle in a Histogram (bonus)	Find the area of the largest rectangle inside a histogram.	Stack
L	Inversion Count (bonus)	Count pairs i < j with a[i] > a[j].	Divide and conquer

Good luck and happy coding!