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IPCTRAIN - Editorial

2
1

PROBLEM LINK:

Practice
Contest

Author: Admin2
Primary Tester: Misha Chorniy
Editorialist: Hussain Kara Fallah

DIFFICULTY:

Easy

PREREQUISITES:

Greedy,Heap

PROBLEM:

You have an upcoming camp. There are N trainers. The camp runs for D days.Each day,there can be at most one lecture. The ith trainer arrives on day Di and then stays till the end of the camp. He also wants to teach exactly Ti lectures. For each lecture that a trainer was not able to teach,his sadness level will be increased by Si. You are the main organizer of the contest. You want to find minimum total sadness of the trainers.

EXPLANATION:

Let's assign our trainers starting from the first day of the camp. At each day adding arriving trainers to our set of trainers.

Each day should be assigned to only one trainer, it's obvious that we should assign the trainer with maximum sadness to this lecture, so our set (container) should be a heap sorting trainers by their sadness value. In fact we should know also the number of days each lecturer wants to serve in, so we take the lecturer with maximum sadness from our heap and decrease his demand by 1. In case he still has lectures he would like to do, we keep him in the heap, otherwise we just pop him out.

After finishing all days, some teachers may have some remaining lectures they wanted to teach but we couldn't find such days for them. Let's denote the number of lectures the ith trainer couldn't teach by remi So our answer would be :

$answer = \sum_{i=1}^{i=N} rem_i * S_i$

AUTHOR'S AND TESTER'S SOLUTIONS:

AUTHOR's solution: Will be found here
TESTER's solution: Will be found here
EDITORIALIST's solution: Will be found here

This question is marked "community wiki".

asked 15 Jul, 07:23

deadwing97's gravatar image

3★deadwing97
118320
accept rate: 0%

edited 20 Jul, 13:50


This question literally screamed "PRIORITY QUEUE" in my ears. One of the good questions which can be solved with knowledge of proper data type!!

Honestly, i saw priority queue code for first time in "Cooking Schedule" editorial (one of the answers told that "it can also be solved using priority queue") and it made life so simple for me here.

My code- https://www.codechef.com/viewsolution/14436208

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answered 17 Jul, 15:30

vijju123's gravatar image

5★vijju123 ♦
11.1k314
accept rate: 18%

2

Solution : Great! Comments : Extraordinary :D

(17 Jul, 15:38) dishant_184★

Lol XD. It just came into my mind when i read "A trainer who comes to the camp stays there till end of camp" :p

(17 Jul, 15:40) vijju123 ♦5★

I have used Segment Trees

Code: https://www.codechef.com/viewsolution/14558413

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answered 17 Jul, 16:52

codeiiitk's gravatar image

1★codeiiitk
111
accept rate: 0%

@lord_ozb: You have used a double loop here which caused the time to exceed the limit.

                for(int i = 0; i < d; i++){
                int x = -1;
                int max = Integer.MIN_VALUE;
                for(int j = 0; j <= i; j++){
                    if(queue[j].size() != 0){
                        Trainer temp = queue[j].peek();
                        if(temp.sad > max){
                            max = temp.sad;
                            x = j;
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answered 18 Jul, 09:05

pro_coder123's gravatar image

4★pro_coder123
211
accept rate: 0%

Can anyone help me? Author solution I seem that complexity O(N*T).Here N=100000 and T=100000 according to Constraints.How it's passed all test case.May be something i miss.Thanks in advance.

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answered 20 Jul, 20:47

aseem_cu's gravatar image

2★aseem_cu
111
accept rate: 0%

solutions are not available yet!!

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answered 17 Jul, 15:20

coderholyy's gravatar image

2★coderholyy
214
accept rate: 0%

@admin The links to the solution are not working! Please check it.

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answered 17 Jul, 15:20

dishant_18's gravatar image

4★dishant_18
47218
accept rate: 7%

community - need help to understand what is missing https://www.codechef.com/viewsolution/14559868. only 40 pts

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answered 17 Jul, 18:58

njr07121977's gravatar image

3★njr07121977
211
accept rate: 0%

Can anyone explain where I went wrong? 40 pts.

https://www.codechef.com/viewsolution/14561290

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answered 17 Jul, 21:26

lord_ozb's gravatar image

3★lord_ozb
313
accept rate: 0%

Hi! The link to practice and main contest are incorrect. Please update.

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answered 18 Jul, 08:32

code_monk_wi's gravatar image

3★code_monk_wi
1
accept rate: 0%

can anyone explain why i m getting WA for last 2 subtask. https://www.codechef.com/viewsolution/14601668

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answered 18 Jul, 09:05

gamessingh866's gravatar image

3★gamessingh866
1
accept rate: 0%

inside practice, contest link is given while in contest, practice session link is given, plz interchange those at top of editorial

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answered 18 Jul, 17:15

hemant_dhanuka's gravatar image

4★hemant_dhanuka
2797
accept rate: 5%

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answered 18 Jul, 17:57

shawnbam_96's gravatar image

4★shawnbam_96
511
accept rate: 0%

practice link is not working..please fix this....

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answered 18 Jul, 18:24

amanharitsh's gravatar image

3★amanharitsh
134
accept rate: 0%

If I solve the above question using heaps as stated, then on popping out the trainer which doesn't have any lecture remaining and at the very same time maintaining the sort would require the complexity O(n). On the other hand if we just extract him from the heap and heapify using time complexity O(lg n) would disturb the sort. How do i proceed?

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answered 18 Jul, 19:37

navdha_98's gravatar image

2★navdha_98
1
accept rate: 0%

use c++ Priority Queue

(19 Jul, 01:28) deadwing973★

Links to practice and competition are backwards.

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answered 19 Jul, 03:18

tao_of_coding's gravatar image

4★tao_of_coding
12
accept rate: 0%

I guess I had gone mad because I couldn't think of such a simple solution. So I did this using segment trees. O(nlog(n)log(n)) https://www.codechef.com/viewsolution/14497188

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answered 19 Jul, 18:25

deadpool_18's gravatar image

4★deadpool_18
0
accept rate: 0%

Links for all tutorials of July long challange for practice and contest seem to be swapped. Please consider correcting them .

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answered 25 Jul, 04:14

aman935's gravatar image

3★aman935
1101
accept rate: 0%

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question asked: 15 Jul, 07:23

question was seen: 2,290 times

last updated: 25 Jul, 04:14