Need help generating a hash table

So hopefully someone here knows something about making hash tables. I have to generate a hash table of load alpha from seq1 which is an array of randomly generated numbers between 0 and 10,000. What I'm having trouble with is actually inserting the numbers into the table. So far my code seems to be getting stuck in a loop or its efficiency is so far gone that my computer cannot produce an answer in a reasonable amount of time. Below is my code for making the hash table where a is the load factor alpha specified by the user (a < 1) and m is the table size, in this case m=9973. Seq1 was created using the randi function.

      function [ T ] = MakeAHashTable(seq1,a,m)
      n = floor(a.*m);
      T = zeros(size(seq1));
      index = 1;
      i = 0; 
      while i <= m || n ~= 0
          k = seq1(index);
          j = mod(k+i,m)+1;
          if T(j) == 0
              T(j) = k;
              index = index+1;
              i = 0;
              n = n-1;
          else i = i+1
          end
      end 
      end

[Nicholas Colburn]

I've found by changing the OR comparison to && that this code does indeed work by inserting the seq1 into T. One quick question would be is there any way to initialize T to contain all null? As of now T is created with all zeroes, but what if 0 is a number in seq1? If I wanted to search for that key later on in my code it would be impossible.

Answer 1

[Walter Roberson]

Where do you change i to be non-zero ?

[Nicholas Colburn]

I've updated my code to reflect where i changes. I had originally used a for loop to insert seq1 and must have forgotten to add the incrementation when I changed to a while loop.

[Walter Roberson]

Please recheck your condition i <= m || n ~= 0 . The loop will not exit until both are true. You decrement n towards 0 as you insert elements towards the loading factor, and you increment i as you find used slots, but since you keep going when n = 0 if i <= m, then as long as you find one free slot in that case you will decrement n to -1 and then after that it will never be 0.

[Nicholas Colburn]

Thank you, I just caught that bug a few minutes ago. I commented on the original post about using null and was wondering if you had any insight to offer on that.

[Walter Roberson]

No, there is no "null" in numeric matrices. The closest you can get is NaN, which is Not A Number. Note that you cannot compare anything to NaN, because NaN == NaN is false and NaN ~= NaN is also false. You must use isnan() to check for NaN.