Solution.go

func movesToChessboard(board [][]int) int {
	n := len(board)
	mask := (1 << n) - 1
	rowMask, colMask := 0, 0
	for i := 0; i < n; i++ {
		rowMask |= board[0][i] << i
		colMask |= board[i][0] << i
	}
	revRowMask := mask ^ rowMask
	revColMask := mask ^ colMask
	sameRow, sameCol := 0, 0
	for i := 0; i < n; i++ {
		curRowMask, curColMask := 0, 0
		for j := 0; j < n; j++ {
			curRowMask |= board[i][j] << j
			curColMask |= board[j][i] << j
		}
		if curRowMask != rowMask && curRowMask != revRowMask {
			return -1
		}
		if curColMask != colMask && curColMask != revColMask {
			return -1
		}
		if curRowMask == rowMask {
			sameRow++
		}
		if curColMask == colMask {
			sameCol++
		}
	}
	f := func(mask, cnt int) int {
		ones := bits.OnesCount(uint(mask))
		if n%2 == 1 {
			if abs(n-ones*2) != 1 || abs(n-cnt*2) != 1 {
				return -1
			}
			if ones == n/2 {
				return n/2 - bits.OnesCount(uint(mask&0xAAAAAAAA))
			}
			return (n+1)/2 - bits.OnesCount(uint(mask&0x55555555))
		} else {
			if ones != n/2 || cnt != n/2 {
				return -1
			}
			cnt0 := n/2 - bits.OnesCount(uint(mask&0xAAAAAAAA))
			cnt1 := n/2 - bits.OnesCount(uint(mask&0x55555555))
			return min(cnt0, cnt1)
		}
	}
	t1 := f(rowMask, sameRow)
	t2 := f(colMask, sameCol)
	if t1 == -1 || t2 == -1 {
		return -1
	}
	return t1 + t2
}

func abs(x int) int {
	if x < 0 {
		return -x
	}
	return x
}