#P2850. [USACO06DEC] Wormholes G

    ID: 1893 远端评测题 1000ms 128MiB 尝试: 0 已通过: 0 难度: 6 上传者: 标签>2006USACO深度优先搜索,DFS负权环

[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 N(1N500)N (1 \le N \le 500) fields conveniently numbered 1N,M(1M2500)1 \sim N, M (1 \le M \le 2500) paths, and W(1W200)W (1 \le W \le 200) 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 F(1F5)F (1 \le F \le 5) of his farms. No paths will take longer than 10,00010,000 seconds to travel and no wormhole can bring FJ back in time by more than 10,00010,000 seconds.

Input Format

Line 11: A single integer, FF. FF farm descriptions follow.

Line 11 of each farm: Three space-separated integers respectively: NN, MM, and WW.

Lines 2M+12 \sim M+1 of each farm: Three space-separated numbers (S,E,T)(S, E, T) that describe, respectively: a bidirectional path between SS and EE that requires TT seconds to traverse. Two fields might be connected by more than one path.

Lines M+2M+W+1M+2 \sim M+W+1 of each farm: Three space-separated numbers (S,E,T)(S, E, T) that describe, respectively: A one way path from SS to EE that also moves the traveler back TT seconds.

Output Format

Lines 1F1 \sim F: 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 11, FJ cannot travel back in time.

For farm 22, FJ could travel back in time by the cycle 12311 \to 2 \to 3 \to 1, arriving back at his starting location 11 second before he leaves. He could start from anywhere on the cycle to accomplish this.