差分约束系统（转）
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J – Invitation Cards（双向最短路）
In the age of television, not many people attend t …
I – Arbitrage
Arbitrage is the use of discrepancies in currency …
H – Cow Contest（Floyd_传递闭包）
N (1 ≤ N ≤ 100) cows, conveniently numbered …
G – MPI Maelstrom
BIT has recently taken delivery of their ne …
F – Wormholes （B-F判负环回路）
While exploring his many farms, Farmer John …
E – Currency Exchange (B_F变形)
Several currency exchange points are working in ou …
D – Heavy Transportation POJ – 1797
Background Hugo Heavy is happy. After the breakdow …
C – Frogger POJ – 2253
Freddy Frog is sitting on a stone in the mi …