Today I have done leetcode's November LeetCoding Challenge with cpp.

November LeetCoding Challenge 22

Description

Flip Columns For Maximum Number of Equal Rows

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.

Example 1:

Input: matrix = [[0,1],[1,1]]
Output: 1
Explanation: After flipping no values, 1 row has all values equal.

Example 2:

Input: matrix = [[0,1],[1,0]]
Output: 2
Explanation: After flipping values in the first column, both rows have equal values.

Example 3:

Input: matrix = [[0,0,0],[0,0,1],[1,1,0]]
Output: 2
Explanation: After flipping values in the first two columns, the last two rows have equal values.

Constraints:

• m == matrix.length
• n == matrix[i].length
• 1 <= m, n <= 300
• matrix[i][j] is either 0 or 1.

Solution

class Solution {
public:
  int maxEqualRowsAfterFlips(vector<vector<int>>& matrix) {
    unordered_map<string, int> frequency;
    for(const auto &row : matrix) {
      string pattern;
      for(auto bit : row) {
        pattern.push_back('0' + bit ^ row[0]);
      } 
      frequency[pattern] += 1;
    }
    
    int answer = 0;
    for(const auto &[_mask, freq] : frequency) {
      answer = max(answer, freq);
    }
    return answer;
  }
};