数学规律 | HJ53 杨辉三角的变形

# 最优解（找规律）
import sys
alt = [2, 3, 2, 4]  # 发现规律，从第三行开始2324循环
for line in sys.stdin:
    n = int(line.strip())
    if n < 3:
        print(-1)
    if n >= 3:
        print(alt[(n - 3) % 4])  # 所以对4求余，映射到上面alt列表中


# 我的代码（10000行时超内存限制）
n = int(input())
M = [[0]*n for _ in range(n)]
pos = -1
for i in range(n):
    for j in range(n-i-1, n):
        if j == n-1-i:
            M[i][j] = 1
            continue
        elif j != n-1:
            M[i][j] = sum(M[i-1][j-1:j+2])
        else:
            M[i][j] = M[i-1][j-1]*2 + M[i-1][j]
        if i==n-1 and pos == -1 and M[i][j]%2==0:
            pos = j+1
print(pos)

用时：25min