#531 - Lonely Pixel I

Medium • View on LeetCode • View on GitHub

Problem Description

Given an m x n picture consisting of black 'B' and white 'W' pixels, return the number of black lonely pixels.

A black lonely pixel is a character 'B' that located at a specific position where the same row and same column don't have any other black pixels.

Solution

/**
 * @param {character[][]} picture
 * @return {number}
 */
var findLonelyPixel = function(picture) {
  const rows = picture.length;
  const cols = picture[0].length;
  const rowCounts = new Array(rows).fill(0);
  const colCounts = new Array(cols).fill(0);
  let result = 0;

  for (let row = 0; row < rows; row++) {
    for (let col = 0; col < cols; col++) {
      if (picture[row][col] === 'B') {
        rowCounts[row]++;
        colCounts[col]++;
      }
    }
  }

  for (let row = 0; row < rows; row++) {
    for (let col = 0; col < cols; col++) {
      if (picture[row][col] === 'B' && rowCounts[row] === 1 && colCounts[col] === 1) {
        result++;
      }
    }
  }

  return result;
};