1946D - Birthday Gift - CodeForces Solution

def solve():
    n, x = map(int, input().split())
    x += 1
    a = list(map(int, input().split()))
    res = -1
    for i in range(30, -1, -1):
        b = []
        open = False
        for j in range(len(a)):
            if not open:
                b.append(a[j])
            else:
                b[-1] ^= a[j]
            if a[j] & (1 << i):
                open = not open
        if not (x & (1 << i)):
            if open:
                print(res)
                return
            a = b
        else:
            if not open:
                res = max(res, len(b))
    print(res)

t = int(input())
for _ in range(t):
    solve()