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Closed 11 years ago.

我试图修改一些速记代码以随机数字为主线。

然而,虽然测试程序并不正确。我不知道为什么这样做。

int random (int num) {
    int random = rand() % (num - 1);
    return random;
}

int* partition (int* first, int* last);
void quickSort(int* first, int* last) {
    if (last - first <= 1) return;

    int* pivot = partition(first, last);
    quickSort(first, pivot);
    quickSort(pivot + 1, last);
}

int* partition (int* first, int* last) {
    //--int pivot = *(last - 1);    
    int* pos = (first + random(last - first));
    int pivot = *pos;
    int* i = first;
    int* j = last - 1;

    for (;;) {
        while (*i < pivot && i < last) i++;
        while (*j >= pivot && j > first) j--;
        if (i >= j) break;
        swap (*i, *j);
    }
    swap (*pos, *i);
    return i;
}

Answer 1

您的 < a href=> https://stackoverflow.com/ questions/10714207/c-quicksort-pivot-optimination> > 第一次执行有效,但是在特定数据集中行为退化。您原始工作代码中的引线为 , 因此最简单的修正是将随机元素与互换。您的原始分区代码的其余部分将保持不变。

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