1.取十組隨機數，每組共200000個數，分別用氣泡排序和快速排序法排序，分別記錄所化時間。

2.程式

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <ctype.h>
//#include <math.h>
FILE *fpt;  //* file point of targe
void exchange(int *a,int *b)
{
    int t=*a;
    *a=*b;
    *b=t;
}
void bubble_sort(int list[],int n)
{
    int i,j;
    for(j=n-1; j>0; j--)
        for(i=0; i<j; i++)
            if(list[i]>list[i+1]) exchange(&list[i],&list[i+1]);
}

void quick_sort(int list[],int left,int right)
{

    if (left<right)
    {
        int i=left; //from left to right
        int j=right; //from right to left
        int mid=(left+right)/2;
        int t=list[mid];; //the base number to compare

        while(1)
        {
            while (list[i]<t) i++;
            while (list[j]>t) j--;
            if(i>=j) break;
            exchange(&list[i++],&list[j--]);
        }
        //  fprintf(fpt,"***\t");
        // for(int a=0; a<40; a++) fprintf(fpt,"%d\t", list[a]);
        //  fprintf(fpt,"***\n\n");
        quick_sort(list,left,i-1);
        quick_sort(list,j+1,right);
    }
}

int main()
{
    clock_t start_time, finish_time; // clock_t is a type of long int.
    double total_time=0;
    time_t t;
    t=time(NULL);
    printf("System time : %s\n",ctime(&t));
    double d1,d2,d3;
    // FILE *fpt;  //* file point of targe
    fpt=stdout;
    unsigned long n=200000;
    if ((fpt = fopen("out.txt", "w+")) == NULL)
    {
        printf("Can't open file :out.txt \n");
        exit(1);
    }
    printf("Calculation started...\n");
    int sint[n],sint2[n];
    for (int c=0;c<10;c++)
    {

        start_time = clock();
        // generate random int
        for (int i=0; i<n; i++)
        {
            srand(time(NULL));
            sint[i]=rand();
            sint2[i]=sint[i];
        }
        finish_time= clock();
        d1 = (double)((finish_time - start_time)) / (double)CLOCKS_PER_SEC;
        fprintf(fpt,"generate: %.12f second\t ",d1);


//bubble sort
        start_time = clock();
        bubble_sort(sint,n);
        finish_time= clock();
        d2 = (double)(finish_time - start_time) / (double)CLOCKS_PER_SEC;
        fprintf(fpt,"bubble sort: %.12f second\t",d2);
// quick sort
        start_time = clock();
        quick_sort(sint2,0,n-1);
        finish_time= clock();
        d3 = (double)(finish_time - start_time) / (double)CLOCKS_PER_SEC;
        fprintf(fpt,"quick sort: %.12f second\t", d3);
        int k=0;
        for(int i=0; i<n; i++)
        {
            if(sint[i]!=sint2[i])
            {
                fprintf(fpt,"~~~position %d is not same.~~~\n",i);
                k++;
            }
        }
        fprintf(fpt,"mismatch: %d \n",k);
        total_time=total_time+d1+d2+d3;
    }
    fprintf(fpt,"total time: %f second\n", total_time);
    fclose(fpt);

    printf("\n\nCalculation finished!Please find results in out.txt.!\n\n");
    t=time(NULL);
    printf("System time : %s\n",ctime(&t));
    getch();
    exit(0);
    return 0;
}
 

4.比較時間

整個程式所化時間為13分15秒，等於795秒，所以統計的total time 應該沒有問題。從兩種方法所花時間上看，快速排序有絕對的優勢。