深度优先遍历--最大的岛屿

a=[[1,1,1,0,0,0],
   [1,1,1,0,0,0],
   [1,0,0,0,1,1],
   [0,1,1,0,1,0],
   [0,1,1,0,0,0]]
area = 0
def maxAreaOfIsland(a):
   #记录地图的行，列 
    row=len(a)
    col=len(a[0])
    for i in range(row):
        for j in range(col):
            if a[i][j]==1:
                #存储当前岛屿的面积
                cur=1
                #深度优先遍历
                dfs(i,j,cur,a)
    return area
def dfs(i,j,cur,a):
    #定义全局变量
    global area
    #将以已经遍历过的标记
    a[i][j]=2
    if i>0 and a[i-1][j]==1:
        cur=dfs(i-1,j,cur+1,a)
    if i<len(a)-1 and a[i+1][j]==1:
        cur = dfs(i+1,j,cur+1,a)
    if j>0 and a[i][j-1]==1:
        cur=dfs(i,j-1,cur+1,a)
    if j<len(a[0])-1 and a[i][j+1]==1:
        cur=dfs(i,j+1,cur+1,a)
    #更新最大面积
    area=max(area,cur)
    return cur
print(maxAreaOfIsland(a))
输出：7            

a=[[1,1,1,0,0,0],
   [1,1,1,0,0,0],
   [1,0,0,0,1,1],
   [0,1,1,0,1,0],
   [0,1,1,0,0,0]]

def maxAreaOfIsland(a):
    global cur
    area = 0
    row=len(a)
    col=len(a[0])
    for i in range(row):
        for j in range(col):
            cur=0
            dfs(i,j,a)
            area=max(cur,area)
    return area

def dfs(i,j,a):
    global cur
    if i<0 or i>len(a)-1 or j<0 or j>len(a[0])-1 or a[i][j]!=1:
        return
    cur+=1
    a[i][j]=2
    dfs(i-1,j,a)
    dfs(i+1,j,a)
    dfs(i,j-1,a)
    dfs(i,j+1,a)
print(maxAreaOfIsland(a))
输出：7