英语翻译Think of this problem instead as one of a random walk al

英语翻译
Think of this problem instead as one of a random walk along a number line.Let 0 be the starting point,p be the probability of moving to the right,and q be the probability of moving to the left.
Let B=probability of ever moving one to the left from where you are.
Let A=probability of revisiting current square from the right.
B = q + Aq + A^2q + A^3q + ...= q/(1-A).
A=pB --> B=A/p --> B=A/(1-q).
q/(1-A) = A/(1-q) --> A=q,1-q.
However,A must be less than or equal to both p and q,thus the reasonable solution is A=min(q,1-q).
A=min(q,1-q).