30D - King's Problem - CodeForces Solution

from bisect import *

n,k=map(int,input().split())
x=list(map(int,input().split()))
sp_y=int(input())

sp_x = x[-1]
start_x = x[k-1]
min_path = float('inf')

x.pop()
x.sort()

x=[x[0]]+x+[x[-1]]

def dist2sp(b):
    if b in [len(x)-1,0,-1]:
        return 0
    return ((sp_x-x[b])**2+sp_y**2)**.5

if k == n+1:
    print(x[-1]-x[0]+min(dist2sp(-2),dist2sp(1)))
    exit()

k=bisect(x,start_x)-1
for i in range(1,len(x)-1):
    if i<=k:
        min_path=min(min_path,min(x[-2]-x[k]+dist2sp(i),x[k]-x[i]+dist2sp(-2))+x[-2]-x[i]+dist2sp(i-1)+x[i-1]-x[1])
    if k<=i:
        min_path=min(min_path,min(x[k]-x[1]+dist2sp(i),x[i]-x[k]+dist2sp(1))+x[i]-x[1]+dist2sp(i+1)+x[-2]-x[i+1])

print(min_path)