#P2850. [USACO06DEC] Wormholes G
[USACO06DEC] Wormholes G
Description
While exploring his many farms, Farmer John has discovered a number of amazing wormholes. A wormhole is very peculiar because it is a one-way path that delivers you to its destination at a time that is BEFORE you entered the wormhole! Each of FJ's farms comprises fields conveniently numbered paths, and wormholes.
As FJ is an avid time-traveling fan, he wants to do the following: start at some field, travel through some paths and wormholes, and return to the starting field a time before his initial departure. Perhaps he will be able to meet himself :) .
To help FJ find out whether this is possible or not, he will supply you with complete maps to of his farms. No paths will take longer than seconds to travel and no wormhole can bring FJ back in time by more than seconds.
Input Format
Line : A single integer, . farm descriptions follow.
Line of each farm: Three space-separated integers respectively: , , and .
Lines of each farm: Three space-separated numbers that describe, respectively: a bidirectional path between and that requires seconds to traverse. Two fields might be connected by more than one path.
Lines of each farm: Three space-separated numbers that describe, respectively: A one way path from to that also moves the traveler back seconds.
Output Format
Lines : For each farm, output YES if FJ can achieve his goal, otherwise output NO.
2
3 3 1
1 2 2
1 3 4
2 3 1
3 1 3
3 2 1
1 2 3
2 3 4
3 1 8
NO
YES
Hint
For farm , FJ cannot travel back in time.
For farm , FJ could travel back in time by the cycle , arriving back at his starting location second before he leaves. He could start from anywhere on the cycle to accomplish this.
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