n=input().split()
a=int(n[0])
head=int(n[1])
key=int(n[2])
m=[[0 for i in range(0,2)] for j in range(0,a+1)]
for i in range(0,a):
    x=input().split()
    m[i][0]=int(x[0])
    m[i][1]=int(x[1])
flag=0
if key<m[head][0]:
    print(key,end=' ')
    flag=1
while head!=-1:
    print(m[head][0],end=' ')
    if key>=m[head][0] and key<=m[m[head][1]][0] and flag==0:
        print(key,end=' ')
        flag=1
    head=m[head][1]
if flag==0:
    print(key)

偷懒链表

class Node:
    def __init__(self,val:int,nxt:int):
        self.val=val
        self.nxt=nxt
def add (it,val):
    a.append(Node(val,a[it].nxt))
    a[it].nxt=len(a)-1
def delete (it):
    a[it].nxt=a[a[it].nxt].nxt
a=[Node(0,0) for i in range(3000)]
e=0
n,h,key=map(int,input().split())
for i in range(n):
    a[i].val,a[i].nxt=map(int,input().split())
    if a[i].nxt==-1:
        e=i
it=h
if a[h].val>=key:
    a.append(Node(key,h))
    h=len(a)-1#特判
if a[e].val<=key:
    add(e,key)#特判
else:
    while it!=-1:
        if a[a[it].nxt].val>=key and a[it].val<=key:
            add(it,key)
            break
        it=a[it].nxt
it=h
while it!=-1:
    print(a[it].val,end=" ")
    it=a[it].nxt

题解qp 代码仅供参考，课上讲的实现方式还是要会的，class写法较好写好理解

课上的

n,head,key=map(int,input().split())
a=[]
for i in range(n):
    x,y=map(int,input().split())
    a.append([x,y])
p=head
pre=-1
a.append([key,-1])
while p!=-1 and key>a[p][0]:
    pre=p
    p=a[p][1]
if pre==-1:
    a[len(a)-1][1]=head
    head=len(a)-1
else:
    a[len(a)-1][1]=a[pre][1]
    a[pre][1]=len(a)-1
p=head
while p!=-1:
    print(a[p][0],end=" ")
    p=a[p][1]