# EXTRACT MIN algorithm for Young tableau

This are two sections from a task I got.

The Young tableau is defined as a matrix of m rows on n columns so that the bars in each row are sorted in ascending order Left to right and the elements in each column are sorted in ascending order from top to bottom. Some of the elements in the Young tableau may be $\infty$ we will refer to these elements as non-existent elements . Therefore, the Young tableau can be used to hold finite numbers.

1. Write an algorithm for EXTRACT-MIN on a non-empty Young tableau of m at n in time running $O(n+m)$
2. Show how to insert a new element into a non-complete Young tableau v at the size of m at n in time running $O(m+n)$

That's what I tried:

When I remove the element at the $(1,1)$ I need to move every element in the table 1 step left (and if the col is 1 so move one row up and put it on the last col) so I can solve it on $O(n*m)$. I think that $O(m+n)$ actually measn $O(max(m,n))$

Regarding the second clause I was thinking to compare the element to insert with the element in the first col in every row until until we get to bigger one and then and then check on this row where to insert it. But again let's say that I want to insert element which will be the min on the new table, so I need to push all the elements one stop left and it takes $O(m*n)$

• Can you clarify what do you mean by insert a single element? Inserting a row or a column is clear but how is a single element inserted? I would insert a single row and column just at the cell where the new element should be placed. And assign all values with inf. If you store your table as a grid of linked list then it takes m + n operation. But I am not sure what you mean. – fade2black Jun 13 '17 at 18:06
• The table is 2D array. Let's say that the elements are numbers and I want to insert a number. – omer adam Jun 13 '17 at 18:52
• Have a look here. It may help you. It says that complexity of insertion is O(max(n,m)). In fact max(n,m) is O(n+m), so there's nothing wrong with it if you say that it is O(n+m). – fade2black Jun 13 '17 at 20:12
• Jeu de taquin might be relevant here. – Yuval Filmus Jun 14 '17 at 6:56

## 2 Answers

Hint: For EXTRACT-MIN, instead of thinking in terms of shifting rows/columns, try to replace the element at $(1,1)$ by $+\infty$. Now you just want to swap $+\infty$ with one of his neighbour until you get the invariant of a Young tableau. How can you decide where to move it?

Here you can take reference from this link, where above stated algo to find the minimum is explained in a simple way: https://www.geeksforgeeks.org/print-elements-sorted-order-row-column-wise-sorted-matrix/

And for Young Tabeleu method, you can refer this link: http://mathworld.wolfram.com/YoungTableau.html

• Welcome to the site! Those links probably do answer the question but we're really looking for actual answers, rather than pointers to answers elsewhere. It would be helpful if you could write a dew sentences summarizing the content of those links so that your answer will still contain useful information if (when!) the links stop working. – David Richerby Feb 25 '18 at 13:24