【广度优先遍历-中等】面试题 16.19. 水域大小

【题目】

【代码】
【方法1】递归方法求解

class Solution:
    def pondSizes(self, land: List[List[int]]) -> List[int]:
        ans=[]
        def dfs(x,y):
            if x>=0 and x<len(land) and y>=0 and y<len(land[0]) and land[x][y]==0:
                land[x][y]=1
                return 1+dfs(x+1,y)+dfs(x-1,y)+dfs(x,y+1)+dfs(x,y-1)+dfs(x-1,y-1)+dfs(x+1,y+1)+dfs(x-1,y+1)+dfs(x+1,y-1)
            return 0

        for i in range(len(land)):
            for j in range(len(land[0])):
                if land[i][j]==0:
                    tmp=dfs(i,j)
                    if tmp:
                        ans.append(tmp)
        ans.sort()
        return ans

【方法2】用栈代替递归

class Solution:
    def pondSizes(self, land: List[List[int]]) -> List[int]:
        ans=[]
        for i in range(len(land)):
            for j in range(len(land[0])):
                if land[i][j]==0:
                    cnt=0
                    stack=[(i,j)]
                    while stack:
                        x,y=stack.pop()
                        if x>=0 and x<len(land) and y>=0 and y<len(land[0]) and land[x][y]==0:
                            land[x][y]=1
                            cnt+=1
                            stack.append((x+1,y))
                            stack.append((x-1,y))
                            stack.append((x,y+1))
                            stack.append((x,y-1))
                            stack.append((x-1,y-1))
                            stack.append((x+1,y+1))
                            stack.append((x-1,y+1))
                            stack.append((x+1,y-1))
                    if cnt:
                        ans.append(cnt)
        ans.sort()
        return ans