columns = []
matrix = [][]

for (i = 0; i < m; i++)
	# i for rows
	setting_zeroes = false
	for (j = 0; j < n; j++)
		# j for columns
		if setting_zeroes:
			matrix[i][j] = 0
			continue
		if matrix[i][j] == 0:
			columns.append(j)
			j = -1
			setting_zeroes = true

foreach (int j in columns) {
	for (i = 0; i < m; i++) {
		matrix[i][j] = 0
	}
}