COVID19B - Editorial

editorial
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53

Some people(including me) might think why 120(5!) is multiplied here. Its just done to prevent t and x have float value. One can use float t,x and remove 120 as well.

54

Can u give the any test case and its correct ans? it will help

1 Like
55

I dont know why this code is getting accepted for n=3.
As here i have just count all the faster atheletes at their left and all the slower athelets at their right.
https://www.codechef.com/viewsolution/37520086

56

4 2 5 3 1 .

In this example for runner no. 3 with velocity 5 He will infect 3,1. But 3 will in turn infect 4(as 4 will cross 3 after a certain time and get infected ). And 1 will in turn infect 2. So total infected for 5 will be 5(3,1,4,2,5).

57

Really now I Understood what was the mistake I was doing the whole time.

58

Can anybody help me why on
INPUT:
1
5
4 3 5 1 2
it gives
OUTPUT:
4 5

Athlete 3(with velocity 5) will never meet any other athlete so it should show 4 4.

59

Brother. cay you please explain this with your approach.

60

I have used dictionary with sets in Python. 30 lines of code.

`t = int(input())

for _ in range(t):
n = int(input())
vels = [int(i) for i in input().split()]

timeCount =  {}
for i in range(n):
    for j in range(i+1, n):
        if vels[i]>vels[j]:
            equalTime = (j-i)/(vels[i]-vels[j])
            equalDist = i + vels[i]*equalTime
            try:
                timeCount[(equalTime, equalDist)].update([i, j])
            except:
                timeCount[(equalTime, equalDist)] = set([i, j])
minVal = None
maxVal = None
timeKeys = sorted(timeCount.keys())
for i in range(n):
    infected = set([i])
    for j in timeKeys:
        if len(infected.intersection(timeCount[j]))!=0:
            infected.update(timeCount[j])
    if minVal==None or len(infected)< minVal:
        minVal = len(infected)
    if maxVal==None or len(infected)> maxVal:
        maxVal = len(infected)
print(minVal, maxVal)`
61

i don’t think 2 will reach 3 here
u sure about it?

62

@alei why did we multiply (j - i) and i by 120 ?
I couldnt find the reasoning behind that please explain .
Thank You

63

Well this question tested mostly the reading skills … if you have read that line " same time same distance " correctly then this question had nothing special to be done… although I would surely agree with what you said it can get the best one down for a while !

64

could you share the code for that bubble sort approach?

65

This post was flagged by the community and is temporarily hidden.

66

Good question tho !

67

Note: order in which I represent speed array will show their relative positions
consider the person with speed 3 is infected
t=0 speed array= 2 3* 1
t=1 speed array= 2 1* 3*
t=2 speed array= 2/1* 3*

68

Can anyone please help me with what’s wrong with this code
https://www.codechef.com/viewsolution/46634584

69

Can you please help me with what’s wrong with this code
https://www.codechef.com/viewsolution/46634584

70

Can you kindly help me with what’s wrong with this code
https://www.codechef.com/viewsolution/46634584

71

[C++] AC Answer without using maps or bubble sort

72

For this test case:
1
4
2 4 0 2
Expected output is given as 2 4 , but I am getting 2 3 . Can anyone verify how we can get 4. I am not able to work out all athletes getting infected…