There were 25 kids in a class and each kid had some best friends. To simplify the problem, let's call each kid by their initial name. Here is a list of each kid's best friends:
a: [l, h]
b: [k, m, i]
c: [f, l, n, j]
d: [g, m, o]
e: [h, n]
f: [c, m, q]
g: [d, n, r, p]
h: [a, k, q, s, o, e]
i: [b, l, r, t]
j: [c, m, s]
k: [u, r, h, b]
l: [u, w, s, i, c, a]
m: [f, b, d, j, t, x, p, v]
n: [y, w, q, g, c, e]
o: [x, r, h, d]
p: [w, m, g]
q: [x, n, h, f]
r: [u, k, g, i, o, y]
s: [v, l, h, j]
t: [w, m, i]
u: [l, r]
v: [k, m, s]
w: [p, l, n, t]
x: [q, m, o]
y: [r, n]
One day all the kids were outside the class room except a
. Then his teacher asked a
to call one of his best friends into room. a
called l
. Then the teacher asked l
to call one of his best friends outside to enter the room, and so on.
After all the call chain, there were no more kids outside, and s
was the last kid called.
Determine the call chain!