常见排序算法

选择排序

void selectSort(vector<int>& array)
{
    size_t length = array.size();
    int i, j;
    int min;
    int t;
    for (i = 0; i < length; i++)
    {
        min = i;
        for (j = i + 1; j < length; j++)
        {
            if (array[j] < array[min])
                min = j;
        }
        if (min != i)
        {
            t = array[min];
            array[min] = array[i];
            array[i] = t;
        }
    }
}

插入排序

void insertSort(vector<int>& array)
{
    size_t length = array.size();
    for (int i = 1; i < length; i++)
    {
        if (array[i - 1] > array[i])
        {
            int tmp = array[i];
            int j = i - 1;
            while (j >= 0 && array[j] > tmp)
            {
                array[j + 1] = array[j];
                j -= 1; 
            }
            array[j + 1] = tmp;
        }
    }
}

希尔排序

void shellSort(vector<int>& array)
{
    size_t length = array.size();
    for (int step = length / 2; step > 0; step /= 2)
    {
        for (int i = step; i < length; i++)
        {
            if (array[i - step] > array[i])
            {
                int tmp = array[i];
                int j = i - step;
                while (j >= 0 && array[j] > tmp)
                {
                    array[j + step] = array[j];
                    j -= step;
                }
                array[j + step] = tmp;
            }
        }
    }
}

归并排序

void mergeSort(vector<int> &array, const int &start, const int &end, vector<int> &tmp)
{
    if (start >= end)
        return;
    int mid = start + (end - start + 1) / 2;
    mergeSort(array, start, mid - 1, tmp);
    mergeSort(array, mid, end, tmp);
    int p1 = start;
    int p2 = mid;
    int pos = start;
    while (p1 < mid || p2 <= end)
    {
        if (p1 == mid)
        {
            while (p2 <= end)
                tmp[pos++] = array[p2++];
        }
        else if (p2 > end)
        {
            while (p1 < mid)
                tmp[pos++] = array[p1++];
        }
        else
        {
            if (array[p1] < array[p2])
                tmp[pos++] = array[p1++];
            else
                tmp[pos++] = array[p2++]; 
        }
    }
    for (int i = start; i <= end; i++)
        array[i] = tmp[i];
}

快速排序

inline void quickSort(vector<int>& array, const int &left, const int & right)
{
    if (left >= right)
        return;

    int tmp = array[left];
    int p1 = left;
    int p2 = right;

    while (p1 != p2)
    {
        while (array[p2] >= tmp && p1 < p2)
            --p2;
        while (array[p1] <= tmp && p1 < p2)
            ++p1;
        if (p1 < p2)
        {
            int t = array[p1];
            array[p1] = array[p2];
            array[p2] = t;
        }
    }

    array[left] = array[p1];
    array[p1] = tmp;

    quickSort(array, left, p1 - 1);
    quickSort(array, p1 + 1, right);
}