滑行问题dfs+记忆存储

import os
import sys

# 请在此输入您的代码
'''
def dfs(grid, i, j, memo):
    if memo[i][j] != -1:
        return memo[i][j]
    
    max_len = 1
    directions = [(-1, 0), (1, 0), (0, -1), (0, 1)]
    for dx, dy in directions:
        ni, nj = i + dx, j + dy
        if 1 <= ni <= n and 1 <= nj <= m and grid[i][j] > grid[ni][nj]:
            current = dfs(grid, ni, nj, memo) + 1
            if current > max_len:
                max_len = current
    
    memo[i][j] = max_len
    return max_len

n, m = map(int, input().split())
grid = [[float('inf')] * (m + 2)]
for _ in range(n):
    row = [float('inf')] + list(map(int, input().split())) + [float('inf')]
    grid.append(row)
grid.append([float('inf')] * (m + 2))

memo = [[-1] * (m + 2) for _ in range(n + 2)]
max_length = 0
for i in range(1, n + 1):
    for j in range(1, m + 1):
        max_length = max(max_length, dfs(grid, i, j, memo))

print(max_length)
'''

def dfs(num,i,j,used):
    if used[i][j] == True: # 当前位置已经遍历过，其最长深度也就是该位置的最长深度
        return res[i][j]
    if num[i][j] <= num[i+1][j] and num[i][j] <= num[i-1][j] and num[i][j] <= num[i][j+1] and num[i][j] <= num[i][j-1] :
        used[i][j] = True
        res[i][j] =1 # 当前位置不能往外移动
    # 搜索上下左右四个位置，并且写入最大值
    if 1<=i+1<=n and num[i][j] > num[i+1][j]:
        if used[i+1][j]:
            res[i][j] = max(res[i][j],res[i+1][j]+1)
        else:
            dfs(num,i+1,j,used)
            used[i+1][j] = True
            res[i][j] = max(res[i][j],res[i+1][j]+1)
    if 1<=i-1<=n  and num[i][j] > num[i-1][j]:
        if used[i-1][j] :
            res[i][j] = max(res[i][j],res[i-1][j]+1)
        else:
            dfs(num,i-1,j,used)
            used[i-1][j] = True
            res[i][j] = max(res[i][j],res[i-1][j]+1)
    if 1<=j+1<=m  and num[i][j] > num[i][j+1]:
        if used[i][j+1]:
            res[i][j] = max(res[i][j],res[i][j+1]+1)
        else:
            dfs(num,i,j+1,used)
            used[i][j+1] = True
            res[i][j] = max(res[i][j],res[i][j+1]+1)
    if 1<=j-1<=m  and num[i][j] > num[i][j-1]:
        if used[i][j-1]:
            res[i][j] = max(res[i][j],res[i][j-1]+1)
        else:
            dfs(num,i,j-1,used)
            used[i][j-1] = True
            res[i][j] = max(res[i][j],res[i][j-1]+1)
    used[i][j] = True
        
n,m = map(int,input().split())
res = [[float('-inf')]*(m+2) for i in range(n+2)]
used = [[False]*(m+2) for i in range(n+2)]
num = []
num.append([float('inf')]*(m+2))

for i in range(n):
    num.append([float('inf')] + list(map(int,input().split()))+[float('inf')])

num.append([float('inf')]*(m+2))
# print(num)
for i in range(1,1+n):
    for j in range(1,1+m):
        dfs(num,i,j,used)
maxlen = 0
for i in range(1,n+1):
    for j in range(1,1+m):
        maxlen = max(maxlen,res[i][j])

print(maxlen)

9.滑行 - 蓝桥云课