Problem:
Score : 300 points

Problem Statement

There are N candles placed on a number line.
The i-th candle from the left is placed on coordinate x_i.
Here, x_1 < x_2 < ... < x_N holds.

Initially, no candles are burning.
Snuke decides to light K of the N candles.

Now, he is at coordinate 0.
He can move left and right along the line with speed 1.
He can also light a candle when he is at the same position as the candle, in negligible time.

Find the minimum time required to light K candles.

Constraints

1 \leq N \leq 10^5

1 \leq K \leq N

x_i is an integer.

|x_i| \leq 10^8

x_1 < x_2 < ... < x_N

Input

Input is given from Standard Input in the following format:

N K
x_1 x_2 ... x_N

Output

Print the minimum time required to light K candles.

Sample Input 1

5 3
-30 -10 10 20 50

Sample Output 1

40

He should move and light candles as follows:

Move from coordinate 0 to -10.

Light the second candle from the left.

Move from coordinate -10 to 10.

Light the third candle from the left.

Move from coordinate 10 to 20.

Light the fourth candle from the left.

Sample Input 2

3 2
10 20 30

Sample Output 2

20

Sample Input 3

1 1
0

Sample Output 3

0

There may be a candle placed at coordinate 0.

Sample Input 4

8 5
-9 -7 -4 -3 1 2 3 4

Sample Output 4

10

Solution in Python (3.4.3) (judge verdict: Accepted)


#とりあえず全検索
iN,iK = [int(_) for _ in input().split()]
aX = [int(_) for _ in input().split()]
aP = [_ for _ in aX if  _ >= 0]
aM = [-1*_ for _ in aX if  _ < 0][::-1]
iP = len(aP)
iM = len(aM)
if iP == 0:
    print(aM[iK-1])
    exit()
elif iM == 0:
    print(aP[iK-1])
    exit()
iD = 2*aP[-1]+2*aM[-1]
for i in range(min(iP-1,iK-1),-1,-1):
    if iK - 2 -i < 0:
        iD = min(iD,aP[i])
    elif iM > iK -2 - i :
        iD = min(iD,aP[i] + 2*aM[iK-i-2])
for i in range(min(iM-1,iK-1),-1,-1):
    if iK - 2 - i < 0:
        iD = min(iD,aM[i])
    elif iP > iK -2 - i :
        iD =  min(iD,aM[i] + 2*aP[iK-i-2])
print(iD)