test3.c

c 的一些经典算法,满好的,适合初学者. 也可以当作小程序看,对初学者会很有帮助

#include "stdio.h"
#include "time.h"

 #define   MAX   300000

test_float_add();
main()
{
  int i;
  unsigned long  j;
  clock_t   start_time,end_time, during_time;

  start_time = clock();
  printf( "start_time=%d",start_time);

  printf("\n");

/****************测试函数主体******************/
    for(j=0; j<3000000000; j++)
     Test_OnlySwitch();

/**********************************************/

  end_time = clock();
  during_time= end_time - start_time;
  printf("end_time=%d",end_time);

  printf("\n\n");

  printf("during_time=%d",during_time);
  getch();

}


/*****************待测函数********************************/
/************************************ ********/
/*比较For 和 While循环效率*/
/*********************************** ********/
 Test_For()
{ 
   int i = 0;
   int j = 0;

   for(i = 0; i < MAX; i++)
   {
      j += i;
   }
}



 Test_While()
{
   int i = 0;
   int j = 0;

   while (i < MAX)
   {
      j += i;
      i++;
   }
}
/*******************************************/
/*比较两层循环嵌套的IF和Switch 效率*/
/*******************************************/
 Test_IF()
{
    int     i;
    unsigned long  j;
    char   release;
       for(j=0;j<MAX;j++)   
       {
                 for(i=0; i<3;i++)
                 {
                 
                           if(i == 0)
                             {
                                release = '1';
                             }
                           else if(i == 1)
                            {
                             release = '1';
                           }else if(i == 2)
                           {
                                   release = '1';
                           }else
                           { 
                               release = '1';
                           }
                    }
           }
}


 Test_Switch()
{
    char  release;
    int  i;
    unsigned long  j;
    for(j=0 ; j<MAX; j++)
    {
                  for(i=0; i<3;i++)
                  {
                           switch (i)
                           {
                              case 0:  
                                 release = '1';
                                 break;
                              case 1:
                                release = '1';
                                 break;
                              case 2:
                                release = '1';
                                 break;
                                default:
                               release = '1';
                                  break;
                            }
                    }
     }
}
/************************************ ********/
/*只有一个单层循环的case语句和If语句的比较*/
/*********************************** ********/
 Test_OnlySwitch()
{
     int i;
    char  release;
    for(i=0; i<3;i++)
    {
                           switch (i)
                           {
                              case 0:  
                                 release = '1';
                                 break;
                              case 1:
                                release = '1';
                                 break;
                              case 2:
                                release = '1';
                                 break;
                                default:
                               release = '1';
                                  break;
                            }
    }             
}
 Test_OnlyIF()
{
    int     i ;
    char   release;
     
                 for(i=0; i<3;i++)
                 {
                 
                           if(i == 0)
                             {
                                release = '1';
                             }
                           else if(i == 1)
                            {
                             release = '1';
                           }else if(i == 2)
                           {
                                   release = '1';
                           }else
                           { 
                               release = '1';
                           }
                    }
           
}