Python题解

import sys
input = lambda:sys.stdin.readline().strip()

ans=0
n,x = map(int,input().split())
a = [0] + list(map(int,input().split()))

i, j = 1, n
while(i<j):
    if a[i] + a[j] == x:
        ans+=1
        i+=1
        continue
    if a[i] + a[j] < x:
        i+=1
        continue
    if a[i] + a[j] > x:
        j-=1
        continue
print(ans)