function [ data, missing_nodes_mapping ] = RemoveRandomNodes( data, num_missing_nodes, missing_nodes_mapping, non_neighbors_distance, missingNodesInput )
%RemoveRandomNodes Remove num_missing_nodes from data. If some nodes are
%removed already, provide missing_nodes_mapping
%   Detailed explanation goes here
graph_size = size(data,1);
max_distance = max(max(data));

% if the mapping is larger than the number of nodes we want to remove, emty
% it and start a new mapping. This can happen if we finished looping over
% the number of missing nodes and started a new iteration of an outer loop.
if size(missing_nodes_mapping,2) > num_missing_nodes
    missing_nodes_mapping = [];
    num_nodes_to_remove = num_missing_nodes;
else
    num_nodes_to_remove = num_missing_nodes - size(missing_nodes_mapping,2);
end

cont = 0;
while cont == 0
    cont = 1;
    
    if nargin < 5
          %randomize a list of nodes to remove and sort it
          if nargin == 2 || size(missing_nodes_mapping,1) == 0
              missing_nodes = sort(ceil(rand(1,num_nodes_to_remove).*graph_size), 'descend');
          else
              missing_nodes = sort( [missing_nodes_mapping(1,:) ceil(rand(1,num_nodes_to_remove).*graph_size)] , 'descend');
          end
          %check if there are doubles in the list
          sizeDiff = size(missing_nodes,2) - size(unique(missing_nodes),2);
          while sizeDiff > 0
              %selecting new nodes randomly until we have enough
              missing_nodes = sort( [unique(missing_nodes)  ceil(rand(1,sizeDiff).*graph_size)] , 'descend');
              sizeDiff = size(missing_nodes,2) - size(unique(missing_nodes),2);
              %fprintf('selected duplicates...\n');
              %cont = 0;
          end
    else
          missing_nodes = missingNodesInput;
    end
    
    %check if we selected one of the nodes which is an
    %outlier, i.e. not connected to any other node
    %TODO: optimize
    %isOutlier = 1;
    
    if cont == 1
        for i = 1:size(missing_nodes,2)
            %check if all the values of this node in the adjacency matrix equal
            %the non_neighbors_distance (except for the diagonal of the matrix)
            %This should not happen if the graph is connected (was an
            %attempt to deal with a corner case)
            while sum(data(missing_nodes(i),:)) - data(missing_nodes(i),missing_nodes(i))  == non_neighbors_distance * (size(data,2) - 1)
                newNode = ceil(rand(1,sizeDiff).*graph_size);
                while ismember(newNode, missing_nodes)
                    newNode = ceil(rand(1,sizeDiff).*graph_size);
                end
                missing_nodes(i) = newNode;
                %isOutlier = 1;
                %fprintf('selected outlier...\n');
            end
            %         for j = 1:size(data, 2)
            %             if data(missing_nodes(i),j) ~= non_neighbors_distance && missing_nodes(i) ~= j
            %                 isOutlier=0;
            %             end
            %         end
        end
    end
    missing_nodes = sort( unique(missing_nodes) , 'descend');
    %     if isOutlier == 1
    %         cont = 0;
    %     end
end

%create a list of the new nodes that each missing node
%is mapped to - each link to a missing node is replaced
%by a link to a new, "UNK" node
missing_nodes_mapping = missing_nodes;

%replace each link to a missing node with a link to a new node

missing_nodes_all_neighbors = zeros(1, size(data,2));
for curr_nissing_node = missing_nodes
      missing_nodes_all_neighbors = missing_nodes_all_neighbors | data(curr_nissing_node,:);
end
missing_nodes_all_neighbors = find(missing_nodes_all_neighbors);

i = 1;
%while i <= size(data,1)
for i = missing_nodes_all_neighbors

    neighbors = find(data(i,:));
    missing_neighbors = intersect(neighbors, missing_nodes);
    missing_neighbors = sort(missing_neighbors, 'descend');
    for curr_missing_neighbor = missing_neighbors
    %for j= 1:size(missing_nodes,2)
        %missing nodes is sorted descending
        %missing_node_idx = missing_nodes(j);
        if data(i,curr_missing_neighbor) == 1
            new_col = ones(size(data, 1), 1) * non_neighbors_distance;
            new_col(i) = 1;
            data = [data new_col];
            new_row =  ones(1,size(data, 2)) * non_neighbors_distance;
            new_row(i) = 1;
            data = [data; new_row];
            data(size(data, 1), size(data,2)) = 0;

            %add the new UNK node to the missing nodes mapping
            %j is the index of the missing node
            %look for the first zero in column j of the
            %missing nodes mapping and put the new node
            %index there
            added_node = 0;
            %add it in the first position which equals zero
            j = find(missing_nodes == curr_missing_neighbor, 1);
            for k = 1 : size(missing_nodes_mapping,1)
                if missing_nodes_mapping(k, j) == 0
                    %if we start with 1000 nodes, and
                    %we have 5 missing nodes, after
                    %adding one node at this point, the
                    %size of the graph is 1001. 5 nodes
                    %will be removed so the correct
                    %index of the new node will be 1001 - 5 = 996.
                    %The next one is 997 and so on.
                    missing_nodes_mapping(k, j) = size(data,1) - num_missing_nodes;
                    added_node = 1;
                    break;
                end
            end
            %if all the column is non-zero, add a new row and put it there
            if added_node == 0
                missing_nodes_mapping = [missing_nodes_mapping; zeros(1, size(missing_nodes_mapping,2))];
                missing_nodes_mapping(size(missing_nodes_mapping,1), j) = size(data,1) - num_missing_nodes;
            end
        end
    end
    %i = i+1;
end


%remove the missing nodes from the matrix
%(missing nodes should be sorted in descending order!!
%so that removing one does not affect the index of the
%others)
for j = 1:size(missing_nodes,2)
    missing_node_idx = missing_nodes(j);
    %     if missing_node_idx == 1
    %         data = data(:, 2 : size(data,2));
    %         data = data(2 : size(data,1), :);
    %     else
    %remove column
    data(:, missing_node_idx) = [];
    %data = [data(:, 1:missing_node_idx-1) data(:,missing_node_idx+1 : size(data,2))];
    %remove row
    data(missing_node_idx, :) = [];
    %data = [data(1:missing_node_idx-1, :); data(missing_node_idx+1 : size(data,1), :)];
    %     end
end

end