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Humanity's Last Code Exam / 2019_H / Hobson’s Trains
Problem
Answer published by the source. Consult the official source to check your work against its answer.
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atcoder
question content
## Problem Statement
Mr. Hobson has retired from running a stable and has invested in a more modern form of transport, trains. He has built a rail network with stations. However, he has retained his commitment to free the passenger from the burden of too many choices: from each station, a passenger can catch a train to exactly one other station. Such a journey is referred to as a leg. Note that this is a one-way journey, and it might not be possible to get back again.
Hobson also offers exactly one choice of ticket, which allows a passenger to travel up to legs in one trip. At the exit from each station is an automated ticket reader (only one, so that passengers do not need to decide which to use). The reader checks that the distance from the initial station to the final station does not exceed legs.
Each ticket reader must be programmed with a list of valid starting stations, but the more memory this list needs, the more expensive the machine will be. Help Hobson by determining, for each station , the number of stations (including ) from which a customer can reach in at most legs.
## Input
The first line of input contains two integers and , where ( ) is the number of stations and ( ) is the maximum number of legs that may be traveled on a ticket. Then follow lines, the th of which contains an integer ( and ), the station which may be reached from station in one leg.
## Output
Output lines, with the th line containing the number of stations from which station can be reached in at most legs.
## Sample Input 1
Plain-text mathematical notation (without MathML)
## Problem Statement Mr. Hobson has retired from running a stable and has invested in a more modern form of transport, trains. He has built a rail network with n stations. However, he has retained his commitment to free the passenger from the burden of too many choices: from each station, a passenger can catch a train to exactly one other station. Such a journey is referred to as a leg. Note that this is a one-way journey, and it might not be possible to get back again. Hobson also offers exactly one choice of ticket, which allows a passenger to travel up to k legs in one trip. At the exit from each station is an automated ticket reader (only one, so that passengers do not need to decide which to use). The reader checks that the distance from the initial station to the final station does not exceed k legs. Each ticket reader must be programmed with a list of valid starting stations, but the more memory this list needs, the more expensive the machine will be. Help Hobson by determining, for each station A, the number of stations (including A) from which a customer can reach A in at most k legs. ## Input The first line of input contains two integers n and k, where n ( 2≤n≤5⋅10⁵ ) is the number of stations and k ( 1≤k≤n−1 ) is the maximum number of legs that may be traveled on a ticket. Then follow n lines, the ith of which contains an integer d_(i) ( 1≤d_(i)≤n and d_(i)≠i ), the station which may be reached from station i in one leg. ## Output Output n lines, with the ith line containing the number of stations from which station i can be reached in at most k legs. ## Sample Input 1
Original LaTeX notation
## Problem Statement Mr. Hobson has retired from running a stable and has invested in a more modern form of transport, trains. He has built a rail network with \( n \) stations. However, he has retained his commitment to free the passenger from the burden of too many choices: from each station, a passenger can catch a train to exactly one other station. Such a journey is referred to as a leg. Note that this is a one-way journey, and it might not be possible to get back again. Hobson also offers exactly one choice of ticket, which allows a passenger to travel up to \( k \) legs in one trip. At the exit from each station is an automated ticket reader (only one, so that passengers do not need to decide which to use). The reader checks that the distance from the initial station to the final station does not exceed \( k \) legs. Each ticket reader must be programmed with a list of valid starting stations, but the more memory this list needs, the more expensive the machine will be. Help Hobson by determining, for each station \( A \), the number of stations (including \( A \)) from which a customer can reach \( A \) in at most \( k \) legs. ## Input The first line of input contains two integers \( n \) and \( k \), where \( n \) ( \( 2 \leq n \leq 5 \cdot 10^5 \) ) is the number of stations and \( k \) ( \( 1 \leq k \leq n - 1 \) ) is the maximum number of legs that may be traveled on a ticket. Then follow \( n \) lines, the \( i \)th of which contains an integer \( d_i \) ( \( 1 \leq d_i \leq n \) and \( d_i \neq i \) ), the station which may be reached from station \( i \) in one leg. ## Output Output \( n \) lines, with the \( i \)th line containing the number of stations from which station \( i \) can be reached in at most \( k \) legs. ## Sample Input 1
Code
6 2
2
3
4
5
4
3
## Sample Output 1
Code
1
2
4
5
3
1
## Sample Input 2
Code
5 3
2
3
1
5
4
## Sample Output 2
Code
3
3
3
2
2
question title
Hobson’s Trains
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