ROS Publish/Subscribe Arrays Example - http://alexsleat.co.uk/2011/07/02/ros-publishing-and-subscribing-to-arrays/

Publish.cpp

#include <stdio.h>
#include <stdlib.h>

#include "ros/ros.h"

#include "std_msgs/MultiArrayLayout.h"
#include "std_msgs/MultiArrayDimension.h"

#include "std_msgs/Int32MultiArray.h"

int main(int argc, char **argv)
{
    

	ros::init(argc, argv, "arrayPublisher");

	ros::NodeHandle n;

	ros::Publisher pub = n.advertise<std_msgs::Int32MultiArray>("array", 100);

	while (ros::ok())
	{
		std_msgs::Int32MultiArray array;
		//Clear array
		array.data.clear();
		//for loop, pushing data in the size of the array
		for (int i = 0; i < 90; i++)
		{
			//assign array a random number between 0 and 255.
			array.data.push_back(rand() % 255);
		}
		//Publish array
		pub.publish(array);
		//Let the world know
		ROS_INFO("I published something!");
		//Do this.
		ros::spinOnce();
		//Added a delay so not to spam
		sleep(2);
	}

}

Subscribe.cpp

#include <stdio.h>
#include <stdlib.h>
#include <vector>
#include <iostream>

#include "ros/ros.h"

#include "std_msgs/MultiArrayLayout.h"
#include "std_msgs/MultiArrayDimension.h"
#include "std_msgs/Int32MultiArray.h"

int Arr[90];
void arrayCallback(const std_msgs::Int32MultiArray::ConstPtr& array);

int main(int argc, char **argv)
{

	ros::init(argc, argv, "arraySubscriber");

	ros::NodeHandle n;	

	ros::Subscriber sub3 = n.subscribe("array", 100, arrayCallback);

	ros::spinOnce();

	for(j = 1; j < 90; j++)
	{
		printf("%d, ", Arr[j]);
	}

	printf("\n");
	return 0;
}

void arrayCallback(const std_msgs::Int32MultiArray::ConstPtr& array)
{

	int i = 0;
	// print all the remaining numbers
	for(std::vector<int>::const_iterator it = array->data.begin(); it != array->data.end(); ++it)
	{
		Arr[i] = *it;
		i++;
	}

	return;
}