Watch 10 video solutions for Lonely Pixel II, a medium level problem involving Array, Hash Table, Matrix. This walkthrough by ThePrimeTime has 1,196,147 views views. Want to try solving it yourself? Practice on FleetCode or read the detailed text solution.
Given an m x n picture consisting of black 'B' and white 'W' pixels and an integer target, return the number of black lonely pixels.
A black lonely pixel is a character 'B' that located at a specific position (r, c) where:
r and column c both contain exactly target black pixels.c, they should be exactly the same as row r.
Example 1:
Input: picture = [["W","B","W","B","B","W"],["W","B","W","B","B","W"],["W","B","W","B","B","W"],["W","W","B","W","B","W"]], target = 3 Output: 6 Explanation: All the green 'B' are the black pixels we need (all 'B's at column 1 and 3). Take 'B' at row r = 0 and column c = 1 as an example: - Rule 1, row r = 0 and column c = 1 both have exactly target = 3 black pixels. - Rule 2, the rows have black pixel at column c = 1 are row 0, row 1 and row 2. They are exactly the same as row r = 0.
Example 2:
Input: picture = [["W","W","B"],["W","W","B"],["W","W","B"]], target = 1 Output: 0
Constraints:
m == picture.lengthn == picture[i].length1 <= m, n <= 200picture[i][j] is 'W' or 'B'.1 <= target <= min(m, n)