백준 1940 주몽 [Python]

참고click

import sys

N = int(sys.stdin.readline())
M = int(sys.stdin.readline()) 

nums = list(map(int, sys.stdin.readline().split()))


nums.sort()
left, right = 0, len(nums)-1
cnt = 0

while left < right:
    sum = nums[left] + nums[right]
    if sum < M:
        left += 1
    elif sum > M:
        right -= 1
    else:
        cnt += 1
        left += 1
        right -= 1

        
print(cnt)