Difference between revisions of "TADM2E 4.9"

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1) Sort the sets (which takes <math>O(n \log{}n)</math>) and use the algorithm described in 2) which takes <math>O(n)</math> (which is also <math>O(n \log{}n)</math>).
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1) Sort the sets (which takes <math>O(n \log{}n)</math>) and use the algorithm described in 2) which takes <math>O(n)</math> (which is also <math>O(n \log{}n)</math>).
  
 
2) A and B are sorted (assume in ascending order). The fact that the sets are sorted implies that there is a comparison defined on the elements of A and B (i.e. we can tell whether an element is greater, equal to or smaller than another element).
 
2) A and B are sorted (assume in ascending order). The fact that the sets are sorted implies that there is a comparison defined on the elements of A and B (i.e. we can tell whether an element is greater, equal to or smaller than another element).

Latest revision as of 18:23, 11 September 2014

1) Sort the sets (which takes $ O(n \log{}n) $) and use the algorithm described in 2) which takes $ O(n) $ (which is also $ O(n \log{}n) $).

2) A and B are sorted (assume in ascending order). The fact that the sets are sorted implies that there is a comparison defined on the elements of A and B (i.e. we can tell whether an element is greater, equal to or smaller than another element).

  • let U be the set which will contain the union
  • while A and B are not empty:
    • if the first element of A is equal to the last element added to U, remove the first element of A and continue with the next iteration
    • if the first element of B is equal to the last element added to U, remove the first element of B and continue with the next iteration
    • if the first (lowest) element of A is strictly smaller than the first (lowest) element of B, remove the first element of A and add it to U, then continue with the next iteration
    • if the first (lowest) element of A is strictly greater than the first (lowest) element of B, remove the first element of B and add it to U, then continue with the next iteration
    • if the first (lowest) element of A is equal to the first (lowest) element of B, remove the first element from each A and B and add one of them to U, then continue with the next iteration
  • After the while loop, either A or B or both are empty. If one of them is non-empty, add its elements to U.