#1072 - Flip Columns For Maximum Number of Equal Rows

Medium • View on LeetCode • View on GitHub

Problem Description

You are given an m x n binary matrix matrix.

You can choose any number of columns in the matrix and flip every cell in that column (i.e., Change the value of the cell from 0 to 1 or vice versa).

Return the maximum number of rows that have all values equal after some number of flips.

Solution

/**
 * @param {number[][]} matrix
 * @return {number}
 */
var maxEqualRowsAfterFlips = function(matrix) {
  const rowPatterns = new Map();
  const rows = matrix.length;
  const cols = matrix[0].length;

  for (let i = 0; i < rows; i++) {
    let pattern = '';
    let flippedPattern = '';
    for (let j = 0; j < cols; j++) {
      pattern += matrix[i][j];
      flippedPattern += 1 - matrix[i][j];
    }
    rowPatterns.set(pattern, (rowPatterns.get(pattern) || 0) + 1);
    rowPatterns.set(flippedPattern, (rowPatterns.get(flippedPattern) || 0) + 1);
  }

  let result = 0;
  for (const count of rowPatterns.values()) {
    result = Math.max(result, count);
  }

  return result;
};