冒泡排序的计时

发布于 2024-10-17 13:18:01 字数 821 浏览 2 评论 0原文

我必须计算冒泡排序需要多长时间并打印它需要多长时间。在我的程序中，打印的时间始终为 0.00 秒。谁能告诉我我做错了什么？

int main()
{
    srand((unsigned)time(NULL));
    int arr[5000], arr2[5000]; 
    int i;
    time_t start, end;
    double timeDiff;

    for(i=0; i < 5000; i++)
    {
        arr[i] = rand() % 100 + 1;
        arr2[i] = arr[i];
    }

    cout << "Here is the initial array:" << endl;
    printArray(arr, 5000);

    time(&start);
    bubbleSort(arr, 5000);
    time(&end);
    timeDiff = difftime(end, start);

    cout << "\nHere is the array after a bubble sort:" << endl;
    printArray(arr, 5000);
    cout << fixed << setprecision(2) << "\nIt took " << timeDiff << " seconds to bubble sort the array." << endl;

    system("pause");
    return 0;
}

原文

I have to time how long a bubble sort takes and print how long it took. In my program the time printed is always 0.00 seconds. Can anyone tell me what I'm doing wrong?

int main()
{
    srand((unsigned)time(NULL));
    int arr[5000], arr2[5000]; 
    int i;
    time_t start, end;
    double timeDiff;

    for(i=0; i < 5000; i++)
    {
        arr[i] = rand() % 100 + 1;
        arr2[i] = arr[i];
    }

    cout << "Here is the initial array:" << endl;
    printArray(arr, 5000);

    time(&start);
    bubbleSort(arr, 5000);
    time(&end);
    timeDiff = difftime(end, start);

    cout << "\nHere is the array after a bubble sort:" << endl;
    printArray(arr, 5000);
    cout << fixed << setprecision(2) << "\nIt took " << timeDiff << " seconds to bubble sort the array." << endl;

    system("pause");
    return 0;
}

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姜生凉生 2024-10-24 13:18:02

我认为您需要使用比 difftime 更精确的东西（仅以秒为单位报告）：

请参阅：C++ 中的时差了解更多信息。

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囚你心 2024-10-24 13:18:02

它的执行速度比更新所需的 CPU 时钟速度还要快。你所要做的就是执行你的排序几百万次，计时，然后将时间除以迭代次数（确保使用双精度数以获得可以获得的最高精度。所以基本上是这样的：

const int runs=1000000;
time(&start);

for(int r=0;r<runs;++r)
    bubbleSort(arr, 5000);

time(&end);
timeDiff = difftime(end, start);

double realduration=timeDiff/(double)runs;

It executes faster than the cpu clock takes to update. What you have to do is execute your sort a couple of million times, time that, and divide the time by the number of iterations (making sure you use a double for the most precision you can get. So basically something like:

const int runs=1000000;
time(&start);

for(int r=0;r<runs;++r)
    bubbleSort(arr, 5000);

time(&end);
timeDiff = difftime(end, start);

double realduration=timeDiff/(double)runs;

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