C/C ++ algorithm learning notes (4)-Exchange Method

Original address: C/C ++ algorithm learning notes (4)-Exchange Method

 

Exchange method:

The procedures of the exchange method are the clearest and simplest. Each time, the current elements are compared and exchanged with the subsequent elements one by one.

#include <iostream.h>void ExchangeSort(int* pData,int Count){    int iTemp;    for(int i=0;i<Count-1;i++)    {        for(int j=i+1;j<Count;j++)        {            if(pData[j]<pData[i])            {               iTemp = pData[i];               pData[i] = pData[j];               pData[j] = iTemp;            }        }    }} void main(){    int data[] = {10,9,8,7,6,5,4};    ExchangeSort(data,7);    for (int i=0;i<7;i++)        cout<<data[i]<<" ";    cout<<"/n";}

 

Before comparison | first time | second time | third time | fourth time | fifth time | sixth time

10 9 8
7
6 5 4

9 10
10 10 10 10 10 10

8
9
9 9 9 9

7 7 7 8 8 8 8

6 6 6 6
7 7 7

5 5 5 5 5
6 6

4 4 4 4 4 5

From the above algorithm, the efficiency is basically the same as that of the bubble method.

Reverse Order (worst case)

First round: 10, 9, 8, 7-> 9, 10, 8, 7-> 8, 10, 9-> 7, 10, 9, 8 (three exchanges)

Round 2: 7, 10, 9-> 7, 9, 10, 8-> 7, 8, 10, 9 (exchange twice)

First round: 7, 8, 10, 9-> 7, 8, 9, 10 (switching once)

Cycles: 6

Number of exchanges: 6

 

Others:

First round:,->, (exchange once)

Round 2: 7, 10, 8, 9-> 7, 8, 10, 9-> 7, 8, 10, 9 (exchange once)

First round: 7, 8, 10, 9-> 7, 8, 9, 10 (switching once)

Cycles: 6

Number of exchanges: 3

 

From the running table, the exchange is almost as bad as the bubble. This is true. The number of loops is also 1/2 * (n-1) * n, so the complexity of the algorithm is still O (N * n ). Because we cannot give all the information, we can only tell you that the exchange is equally bad (in some cases, slightly better, in some cases ).