ak日记 831 dxm

import sys
from math import inf
line = sys.stdin.readline().strip()
vs = list(map(int, line.split()))
n, k = vs[0], vs[1]
line = sys.stdin.readline().strip()
vs = list(map(int, line.split()))
dp = [[0]*n for _ in range(n)]
ans = 0
for i in range(n-1, -1, -1):
    dp[i][i] = (vs[i], vs[i])
    if k==1: ans+=1
    for j in range(i+1, n):
        minv, maxv = dp[i+1][j]
        minv = min(minv, vs[i])
        maxv = max(maxv, vs[i])
        dp[i][j] = (minv, maxv)
        if minv*k == maxv:ans += 1
print(ans)
        
        

import sys
from math import inf
from functools import lru_cache


class Solution:
    def slove(self, n, m, k, x, grid):
        @lru_cache(None)
        def dfs(i=0, j=0, total=0):
            ans = False
            if i == n - 1 and j == m - 1 and total + grid[i][j] == x:
                ans = True
            if i < n and j < m:
                ans = ans or dfs(i + 1, j, total + grid[i][j])
                ans = ans or dfs(i, j + 1, total + grid[i][j])
            return ans

        return dfs()


sol = Solution()
T = int(sys.stdin.readline().strip())
for _ in range(T):
    line = sys.stdin.readline().strip()
    vs = list(map(int, line.split()))
    n, m, k, x = vs[0], vs[1], vs[2], vs[3]
    grid = []
    for _ in range(n):
        line = sys.stdin.readline().strip()
        vs = list(map(int, line.split()))
        grid.append(vs)
    if (sol.slove(n, m, k, x, grid)):
        print("yes")
    else:
        print("no")

import sys
from math import inf
MOD = 10**9+7
n = int(sys.stdin.readline().strip())
dp = [[[0]*2 for _ in range(2)] for _ in range(n+1)]
#dp[i][j][k] i位以 j k=0非1 j k=1 1结尾的最大个数 00 01 10 11
dp[1] = [[8, 1], [0, 0]]
for i in range(2, n+1):
    dp[i][0][0] = ((dp[i-1][0][0] + dp[i-1][1][0])*8)%MOD
    dp[i][0][1] = (dp[i-1][0][0])%MOD
    dp[i][1][0] = (dp[i-1][0][1]*8)%MOD
    dp[i][1][1] = 0
ans = sum([sum(dp[-1][i]) for i in range(2)])%MOD
print(ans)

比较简单 不到一小时选择+算法就做完了～