常用排序算法实现

按平均时间将排序分为四类：

（1）平方阶(O(n2))排序
    　一般称为简单排序，例如直接插入、直接选择和冒泡排序；

（2）线性对数阶(O(nlgn))排序
    　如快速、堆和归并排序；

（3）O(n1+￡)阶排序
    　￡是介于0和1之间的常数，即0<￡<1，如希尔排序；

（4）线性阶(O(n))排序
    　如桶、箱和基数排序。

各种排序方法比较

     简单排序中直接插入最好，快速排序最快，当文件为正序时，直接插入和冒泡均最佳。


影响排序效果的因素

    　因为不同的排序方法适应不同的应用环境和要求，所以选择合适的排序方法应综合考虑下列因素：
　　①待排序的记录数目n；
　　②记录的大小(规模)；
　　③关键字的结构及其初始状态；
　　④对稳定性的要求；
　　⑤语言工具的条件；
　　⑥存储结构；
　　⑦时间和辅助空间复杂度等。

#include <stdio.h>#include<iostream>using namespace std;//交换void swap(int& a, int& b){    int temp = a;    a = b;    b = temp;}//不用中间数的交换  ^按位异或 不相同才为真void swap_(int& a, int& b){    if (a != b)    {        a ^= b;        b ^= a;        a ^= b;    }}//选择排序void select_sort(int *array, int left, int right){    if (NULL == array || left >= right) return;        for (int i=left; i<right; ++i)    {        for (int j=i+1; j<right; ++j)        {            if (array[i] > array[j])            {                swap(array[i], array[j]);            }        }    }}//冒泡排序void bubble_sort(int *array, int left, int right){    if (NULL == array || left >= right) return;    bool flag = false;    for (int i=left; i<right; ++i)    {        for (int j=left+1; j<right-i; ++j)        {            if (array[j-1] > array[j])            {                swap(array[j-1], array[j]);                flag = true;            }        }        if (!flag) return;    }}//插入排序void insert_sort(int *array, int left, int right){    if (NULL == array || left+1 >= right) return;    for (int i= left + 1; i<right; i++)    {        if (array[i - 1] > array[i])        {            int temp = array[i];            int j = i;            while (j > left && array[j - 1] > temp)            {                array[j] = array[j - 1];                j--;            }            array[j] = temp;        }    }}//希尔排序void shell_sort(int* array, int left, int right){    if (NULL == array || left+1 > right) return;    int gap;    for (gap=(right-left)/2; gap>0; gap/=2)    {        for (int i=gap; i<right; ++i)        {            if (array[i - gap] > array[i])            {                int temp = array[i];                int j = i - gap;                for (; j >= 0 && array[j] > temp; j -= gap)                {                    array[j + gap] = array[j];                }                array[j + gap] = temp;            }        }    }}int adjust_array(int* array, int left, int right){    if (NULL == array || left >= right) return 0;    int i = left;    int j = right;    int pos = left;    while(j > i)    {        while(j > i)        {            if (array[j] < array[pos])//从右向左找小于基准数，找到则交换位置            {                swap(array[j], array[pos]);                pos = j;                break;            }            j--;        }        while(j > i)        {            if (array[i] > array[pos])//从左向右找大于基准数，找到则交换位置            {                swap(array[i], array[pos]);                pos = i;                break;            }            i++;        }    }    return pos;}//快速排序void quick_sort(int* array, int left, int right){    if (NULL == array || left >= right) return;    int pos = adjust_array(array, left, right);    quick_sort(array, left, pos-1);    quick_sort(array, pos+1, right);}int get_left(int pos){    return (2*pos + 1);}int get_right(int pos){    return (2*pos + 2);}int get_parent(int pos){    return int(float(pos - 1)/2);}void adjust_heap(int* array, int i, int n){    if (NULL == array || i >= n) return;    int left = get_left(i);    int right = get_right(i);    int large = i;    if (left < n && array[left] > array[large])    {        large = left;    }    if (right < n && array[right] > array[large])    {        large = right;    }    if (large != i)    {        swap(array[large], array[i]);        adjust_heap(array, large, n);    }}void build_heap(int* array, int n){    if (NULL == array || n <= 1) return;    for (int i = n/2 - 1; i >= 0; --i)    {        adjust_heap(array, i, n);    }}//堆排序void heap_sort(int* array, int n){    if (NULL == array || n <= 1) return;        build_heap(array, n);    for (int i = n - 1; i > 0; --i)    {        swap(array[0], array[i]);        adjust_heap(array, 0, i);    }}void merge_array(int* array, int left, int mid, int right){    if (left > right || left > mid || mid > right) return;    int i = left;    int j = mid+1;    int k = 0;    int* temp = new int[right - left + 1];    if (NULL == temp) return;        int m = mid;    int n = right;    while(i <= m && j <= n)    {        if (array[i] > array[j])            temp[k++] = array[j++];        else            temp[k++] = array[i++];    }    while(i <= m)    {        temp[k++] = array[i++];    }    while(j <= n)    {        temp[k++] = array[j++];    }    for (int i=0; i<k; ++i)    {        array[left+i] = temp[i];    }    if (NULL != temp)    {        delete []temp;    }}void _merge_sort(int* array, int left, int right){    if (NULL == array) return;    if (left < right)    {        int mid = (left + right)/2;        _merge_sort(array, left, mid);        _merge_sort(array, mid+1, right);        merge_array(array, left, mid, right);    }}//归并排序void merge_sort(int* array, int n){    if (NULL == array || n <= 1) return;    _merge_sort(array, 0, n-1);}void main(){    int array[] = {4, 6, 3, 2, 90, 45, 23};    int length = sizeof(array)/sizeof(array[0]);    cout<<"sizeof array: "<<length<<endl;    cout<<"sort before:"<<endl;    for (int i=0; i<length; ++i){        cout<<array[i]<<"\t";    }    cout<<endl;    cout<<"请输入你要排序的算法："<<endl;    cout<<"1 选择排序"<<endl;    cout<<"2 冒泡排序"<<endl;    cout<<"3 插入排序"<<endl;    cout<<"4 希尔排序"<<endl;    cout<<"5 快速排序"<<endl;    cout<<"6 堆排序"<<endl;    cout<<"7 归并排序"<<endl;        int n;    cin>>n;    switch (n)    {    case 1:        select_sort(array, 0, length);        break;    case 2:        bubble_sort(array, 0, length);        break;    case 3:        insert_sort(array, 0, length);    break;    case 4:        shell_sort(array, 0, length);        break;    case 5:        quick_sort(array, 0, length - 1);        break;    case 6:        heap_sort(array, length);        break;    case 7:        merge_sort(array, length);        break;    default:        break;    }        cout<<"sort latter:"<<endl;    for (int i=0; i<length; ++i){        cout<<array[i]<<'\t';    }}