**Solution**

**Lonely Pixel I** https://leetcode.com/problems/lonely-pixel-i/#/description

```
from collections import defaultdict
class Solution(object):
def findLonelyPixel(self, picture):
"""
:type picture: List[List[str]]
:rtype: int
"""
if picture == []:
return
self.rows, self.cols = defaultdict(int), defaultdict(int)
items = []
N,M = len(picture), len(picture[0])
for i in range(N):
for j in range(M):
if picture[i][j] == "B":
self.rows[i] += 1
self.cols[j] += 1
items.append((i,j))
cnt = 0
for i,j in items:
if i in self.rows and self.rows[i] == 1 and j in self.cols and self.cols[j] == 1:
cnt += 1
return cnt
```