백준 2170 [선 긋기] 파이썬

https://www.acmicpc.net/problem/2170

#백준 2170 선 긋기
import sys

N=int(sys.stdin.readline())
ans=0
last_end=-1000000000
pos=[]
for _ in range(N):
    a,b=map(int,sys.stdin.readline().split())
    if b<a:
        a,b=b,a
    pos.append([a,b])

pos=sorted(pos, key= lambda x: [x[0],-x[1]])


for val in pos:
    start,end=val
    if start>=last_end:
        ans+=end-start
        last_end=end
    elif end>last_end:
        ans+=end-last_end
        last_end=end

print(ans)