题解 | #滑雪#

def dfs(i,j,length):
    global long
    long = max(long, length)    
    for nx,ny in [(1,0),(0,1),(-1,0),(0,-1)]:
        x = i+nx
        y = j+ny
        if 0<=x<r and 0<=y<c and g[x][y]<g[i][j] and not tag[x][y]:
            tag[x][y]=True
            dfs(x,y,length+1)
            tag[x][y]=False

r,c = list(map(int,input().split()))
g=[]
for i in range(r):
    g.append(list(map(int,input().split())))

long=0
for i in range(r):
    for j in range(c):
        tag = [[False]*c for _ in range(r)]
        tag[i][j]=True
        dfs(i,j,1)
print(long)