782. Transform to Chessboard LeetCode Solution

In this guide, you will get 782. Transform to Chessboard LeetCode Solution with the best time and space complexity. The solution to Transform to Chessboard problem is provided in various programming languages like C++, Java, and Python. This will be helpful for you if you are preparing for placements, hackathons, interviews, or practice purposes. The solutions provided here are very easy to follow and include detailed explanations.

Problem Statement
Complexity Analysis
Transform to Chessboard solution in C++
Transform to Chessboard solution in Java
Transform to Chessboard solution in Python
Additional Resources

782. Transform to Chessboard LeetCode Solution image

Problem Statement of Transform to Chessboard

You are given an n x n binary grid board. In each move, you can swap any two rows with each other, or any two columns with each other.
Return the minimum number of moves to transform the board into a chessboard board. If the task is impossible, return -1.
A chessboard board is a board where no 0’s and no 1’s are 4-directionally adjacent.

Example 1:

Input: board = [[0,1,1,0],[0,1,1,0],[1,0,0,1],[1,0,0,1]]
Output: 2
Explanation: One potential sequence of moves is shown.
The first move swaps the first and second column.
The second move swaps the second and third row.

Example 2:

Input: board = [[0,1],[1,0]]
Output: 0
Explanation: Also note that the board with 0 in the top left corner, is also a valid chessboard.

Example 3:

Input: board = [[1,0],[1,0]]
Output: -1
Explanation: No matter what sequence of moves you make, you cannot end with a valid chessboard.

Constraints:

n == board.length
n == board[i].length
2 <= n <= 30
board[i][j] is either 0 or 1.

Complexity Analysis

Time Complexity: O(n^2)
Space Complexity: O(1)

782. Transform to Chessboard LeetCode Solution in C++

class Solution {
 public:
  int movesToChessboard(vector<vector<int>>& board) {
    const int n = board.size();
    int rowSum = 0;
    int colSum = 0;
    int rowSwaps = 0;
    int colSwaps = 0;

    for (int i = 0; i < n; ++i)
      for (int j = 0; j < n; ++j)
        if (board[0][0] ^ board[i][0] ^ board[0][j] ^ board[i][j] == 1)
          return -1;

    for (int i = 0; i < n; ++i) {
      rowSum += board[0][i];
      colSum += board[i][0];
    }

    if (rowSum != n / 2 && rowSum != (n + 1) / 2)
      return -1;
    if (colSum != n / 2 && colSum != (n + 1) / 2)
      return -1;

    for (int i = 0; i < n; ++i) {
      rowSwaps += board[i][0] == (i & 1);
      colSwaps += board[0][i] == (i & 1);
    }

    if (n % 2 == 1) {
      if (rowSwaps % 2 == 1)
        rowSwaps = n - rowSwaps;
      if (colSwaps % 2 == 1)
        colSwaps = n - colSwaps;
    } else {
      rowSwaps = min(rowSwaps, n - rowSwaps);
      colSwaps = min(colSwaps, n - colSwaps);
    }

    return (rowSwaps + colSwaps) / 2;
  }
};
/* code provided by PROGIEZ */

782. Transform to Chessboard LeetCode Solution in Java

class Solution {
  public int movesToChessboard(int[][] board) {
    final int n = board.length;
    int rowSum = 0;
    int colSum = 0;
    int rowSwaps = 0;
    int colSwaps = 0;

    for (int i = 0; i < n; ++i)
      for (int j = 0; j < n; ++j)
        if ((board[0][0] ^ board[i][0] ^ board[0][j] ^ board[i][j]) == 1)
          return -1;

    for (int i = 0; i < n; ++i) {
      rowSum += board[0][i];
      colSum += board[i][0];
    }

    if (rowSum != n / 2 && rowSum != (n + 1) / 2)
      return -1;
    if (colSum != n / 2 && colSum != (n + 1) / 2)
      return -1;

    for (int i = 0; i < n; ++i) {
      if (board[i][0] == (i & 1))
        ++rowSwaps;
      if (board[0][i] == (i & 1))
        ++colSwaps;
    }

    if (n % 2 == 1) {
      if (rowSwaps % 2 == 1)
        rowSwaps = n - rowSwaps;
      if (colSwaps % 2 == 1)
        colSwaps = n - colSwaps;
    } else {
      rowSwaps = Math.min(rowSwaps, n - rowSwaps);
      colSwaps = Math.min(colSwaps, n - colSwaps);
    }

    return (rowSwaps + colSwaps) / 2;
  }
}
// code provided by PROGIEZ

782. Transform to Chessboard LeetCode Solution in Python

class Solution:
  def movesToChessboard(self, board: list[list[int]]) -> int:
    n = len(board)

    if any(board[0][0] ^ board[i][0] ^ board[0][j] ^ board[i][j]
           for i in range(n) for j in range(n)):
      return -1

    rowSum = sum(board[0])
    colSum = sum(board[i][0] for i in range(n))

    if rowSum != n // 2 and rowSum != (n + 1) // 2:
      return -1
    if colSum != n // 2 and colSum != (n + 1) // 2:
      return -1

    rowSwaps = sum(board[i][0] == (i & 1) for i in range(n))
    colSwaps = sum(board[0][i] == (i & 1) for i in range(n))

    if n % 2 == 1:
      if rowSwaps % 2 == 1:
        rowSwaps = n - rowSwaps
      if colSwaps % 2 == 1:
        colSwaps = n - colSwaps
    else:
      rowSwaps = min(rowSwaps, n - rowSwaps)
      colSwaps = min(colSwaps, n - colSwaps)

    return (rowSwaps + colSwaps) // 2
 # code by PROGIEZ