In the famous card-collecting game
Hearthstone, there is an exciting card named
Yogg Saron, Master of Fate, with a battlecry effect of "If you've cast
10 spells during the game, spin the Wheel of Yogg Saron!"
Six distinct options are contained in the Wheel of Yogg Saron, with a probability of being chosen for each option. Among all options, the one with the least probability of being chosen is "Rod of Roasting." However, this option also has the most devastating effect: Randomly cast "Pyroblast" until a pla
yer dies! Here, "Pyroblast" is a spell of mage class, with the effect of dealing 10 damage to some unit.
Now, given the health point of you and your opponent and the health point of minions on the board, you want to know: If now a battlecry of Yogg Saron, Master of Fate is triggered and the option of "Rod of Roasting" is chosen, what is the probability of you surviving the pyroblasts and winning the game?
Formally, assume your health point is A(A>0), and the health point of at most7 minions on your board are a1,a2,…,a7(ai≥0,ai=0 iff this minion doesn’t exist), respectively. Also, your opponent's health point is B(B>0) and the health point of at most 7 minions on your opponent's board are b1,b2,…,b7(bi≥0,bi=0 iff this minion doesn’t exist), respectively. The option of "Rod of Roasting" is equivalent to the following stochastic process:
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Repeat until A≤0 or B≤0: Choose from A,B,a1,a2,…,a7,b1,b2,…,b7 an element x greater than zero uniformly at random and set x←x−10
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If B≤0, you win. Otherwise, your opponent wins.