9.23 网易笔试

1. 直接判断

t = int(input())
def run():
    n = int(input())
    a = list(map(int, input().split()))
    if n % 2 != 0:
        return True
    x = []
    y = []
    for i in range(len(a)):
        if i % 2 == 0:
            x.append(a[i])
        else:
            y.append(a[i])
    x = list(reversed(sorted(x)))
    y = list(reversed(sorted(y)))
    a = [0]
    while len(x) > 0 or len(y) > 0:
        if len(x) > 0:
            t = x.pop()
            if t < a[-1]:
                return False
            a.append(t)
        if len(y) > 0:
            t = y.pop()
            if t < a[-1]:
                return False
            a.append(t)
    return True
for _ in range(t):
    if run():
        print("YES")
    else:
        print("NO")

2. 直接哈希表

n = int(input())
d = {}
for _ in range(n):
    s = str(sorted(input()))
    if s not in d:
        d[s] = 1
    else:
        d[s] += 1
result = 0
for e in d.values():
    result += (e * (e - 1)) // 2
print(result)

3. 直接计算

m = 10**9 + 7
n = int(input())
a = list(map(int, input().split()))
s = 0
for i in a:
    s += i
mod = n * m
s %= mod
f = 1
for _ in range(n):
    f = f * 2
    f %= mod
f = (f + mod - 1) % mod
u = (f * s) % mod
if u % n == 0:
    print(u // n)
else:
    u %= m
    n %= m
    for i in range(1, 10**6):
        t = (u + (i * m))
        if t % n == 0:
            print(t // n)
            break

4. 暴力，TLE 了