Merge and sort ---- JAVA Implementation

Mergesort)

1,Thoughts:

Multiple times, two or more ordered tables are merged into a new ordered table.

 

2,Algorithm time complexity
In the best case: a merge operation requires n times and a total of N logstores, so it is O (n * logn)
In the worst case, it is O (n * logn) near the average)
Note: For files with a length of N, logn dual-path merge is required, and the time for each merge is O (n ), therefore, the time complexity is O (nlgn) in both the best and worst cases ).

3,Stability

Merge Sorting is a stable sorting algorithm. In the merge process, the relative position of the elements is not changed. 
4. The disadvantage is that it requires extra O (n) space. HoweverIt is suitable for sorting multiple linked lists. 

 

/**

* @ Author Administrator

* Parallel sorting

*/

Public class mergesort {

 

/**

* @ Param ARGs

*/

Public static void main (string [] ARGs ){

Int [] DATA = {1, 7, 16, 21, 41, 46, 52 };

Mergesort (data, 0, Data. Length-1 );//

Printdata (data );

 

}

 

 

 

Private Static void mergesort (INT [] data, int low, int high ){

If (low> = high ){

Return;

}

 

Int mid = (low + high)/2;

Mergesort (data, low, mid );

Mergesort (data, Mid + 1, high );

Merge (data, low, mid, high );

}

 

Private Static void merge (INT data [], int low, int mid, int high ){

Int [] temp = new int [High-low + 1];

Int key = 0;

 

Int I = low;

Int J = Mid + 1;

/** Consider data from low to high as two arrays separated from mid

* Traverse the two arrays separately and put the minimum value into the temporary array.

**/

For (; I <= Mid & J <= high; key ++ ){

If (data [I]> data [J]) {

Temp [Key] = data [J];

J ++;

} Else {

Temp [Key] = data [I];

I ++;

}

}

 

/** If the traversal is complete from data [low] to data [Mid], the values from data [min + 1] to data [High] may not be completely traversed.

* These values must be larger than data [Mid] and are ordered. You can append them directly to temp */

If (I> mid ){

While (j <= high ){

Temp [Key] = data [J];

Key ++;

J ++;

}

}

/** Likewise */

If (j> high ){

While (I <= mid ){

Temp [Key] = data [I];

Key ++;

I ++;

}

}

 

 

/** Return the value of the temp array to the data array */

Setdata (data, temp, low );

}

 

Private Static void setdata (INT [] data, int [] temp, int low ){

If (data. Length <temp. Length ){

Return;

} Else {

For (INT I = 0; I <temp. length; I ++ ){

Data [Low + I] = temp [I];

}

}

}

 

Public static void printdata (INT [] data ){

For (int I: Data ){

System. Out. Print (I + "");

}

System. Out. println ();

}

}