Question

我是Java的新手，我无法理解一个概念。在这段代码中，我需要添加一个交换计数并比较计数，这是我到目前为止所得到的。

public static void SelectionSort ( int [ ] num, int howmany )

{

    int i, j, first, temp;  
    int compCount;
    int swapCount;


    for ( i = num.length - 1; i > 0; i-- )  
    {
        compCount = 0;
        swapCount = 0;
        first = 0;   //initialize to subscript of first element
        for(j = 1; j <= i; j ++)   //locate smallest element between positions 1 and i.
        {
            compCount++;
            if( num[ j ] < num[ first ] )         
                first = j;
         }
         temp = num[ first ];   //swap smallest found with element in position i.
         num[ first ] = num[ i ];
         num[ i ] = temp; 
         swapCount++; 

     }    

     System.out.println("selection sort " + compCount + swapCount );

Answer 1

    public static void SelectionSort ( int [ ] num, int howmany )

    {

        int i, j, first, temp;  
      int compCount = 0;
      int swapCount = 0;


     for ( i = num.length - 1; i > 0; i-- )  
     {
/* you should not be reinitializing swap count and compCount inside the for loop. What this does is make it 0 after each iteration which is not what you want*/
          first = 0;   //initialize to subscript of first element
          for(j = 1; j <= i; j ++)   //locate smallest element between positions 1 and i.
          {
               compCount++;
               if( num[ j ] < num[ first ] )         
                 first = j;
          }
          temp = num[ first ];   //swap smallest found with element in position i.
          num[ first ] = num[ i ];
          num[ i ] = temp; 
          swapCount++; 

      }    

          System.out.println("selection sort " + compCount + swapCount );

Answer 2

由于在每次迭代中清除了计数器，因此无法工作计数器应在开始时初始化，而不是仅增加
这段代码应该更好，但没有经过测试

public static void SelectionSort ( int [ ] num, int howmany )
{
    int i, j, first, temp;  
    int compCount=0;
    int swapCount=0;
    for ( i = num.length - 1; i > 0; i-- )  
    {
        first = 0;   //initialize to subscript of first element
        for(j = 1; j <= i; j ++)   //locate smallest element between positions 1 and i.
        {
            compCount++;
            if( num[ j ] < num[ first ] )         
              first = j;
        }
        temp = num[ first ];   //swap smallest found with element in position i.
        num[ first ] = num[ i ];
        num[ i ] = temp; 
        swapCount++; 
    }
    System.out.println("selection sort " + compCount + swapCount ); 
}

Answer 3

class ssort {
    static void selection_sort(int arr[], int n)
    {
        int swap=0;
        for(int i=0;i<n;i++)
        {
            //find min
            int min_indx=i;
            int old_min=min_indx;
            for(int j=i+1;j<n;j++)
            {
                if(arr[j]< arr[min_indx]){
                    min_indx=j;
                }
            }
            if(old_min != min_indx)
            {
                int temp= arr[min_indx];//swap`enter code here`
                arr[min_indx]=arr[i];
                arr[i]=temp;
                swap++;                         
            }
        }
            System.out.println("Total Swaps "+swap);

    }
    public static void main(String[] args) {
        int arr[]=new int[]{7, 1, 3, 2, 4, 5, 6};
        int n=arr.length;
        selection_sort(arr, n);
        for(int i=0;i<n;i++)
            System.out.print(arr[i]+" ");
    }
}

计算交换计数并在选择排序中进行比较

3 个答案: