常用排序算法

参考如下链接：

http://blog.csdn.net/hguisu/article/details/7776068

#include <iostream>
#include <memory.h>
using namespace std;

void print(int a[], int n){
    for(int j= 0; j<n; j++){
        cout<<a[j] <<"  ";
    }
    cout<<endl;
}

//直接插入排序
void InsertSort(int a[], int n)
{
    int i, j, tmp;
    for (i = 1; i < n; ++i)
    {
        if (a[i] < a[i - 1])
        {
            tmp = a[i];
            for (j = i - 1; j >= 0 && tmp < a[j]; --j)
            {
                a[j + 1] = a[j];
            }
            a[j + 1] = tmp;
        }
    }
    return;
}

void InsertSort1(int a[], int n)
{
    int i, j, tmp;
    for (i = 1; i < n; ++i){
        tmp = a[i];
        for (j = i; j > 0 && tmp < a[j - 1]; --j){
            a[j] = a[j - 1];
        }
        a[j] = tmp;
    }
    return;
}

//希尔排序
void ShellSort(int a[], int n)
{
    int i, j, tmp, increment;
    for (increment = n / 2; increment > 0; increment /= 2)
    {
        for (i = increment; i < n; ++i)
        {
            if (a[i] < a[i - increment])
            {
                tmp = a[i];
                for (j = i; j >= increment; j -= increment)
                {
                    if (tmp < a[j - increment])
                    {
                        a[j] = a[j - increment];
                    }
                    else
                    {
                        break;
                    }
                }
                a[j] = tmp;
            }

        }
    }
    return;
}

//选择排序
void SelectSort(int a[], int n)
{
    int min = 0;
    int tmp = 0;
    for (int i = 0; i < n; ++i){
        min = i;
        for (int j = i + 1; j < n; ++j){
            if (a[j] < a[min]){
                min = j;
            }
        }
        if (min != i){
            tmp = a[min];
            a[min] = a[i];
            a[i] = tmp;
        }
    }
    return;
}

//二元选择排序
void TwoSelectSort(int a[], int n)
{
    int i = 0;
    int j = 0;
    int min = 0;
    int max = 0;
    int tmp = 0;
    for (i = 0; i <= n / 2; ++i){
        min = i;
        max = i;
        for (j = i + 1; j < n - i; ++j){
            if (a[j] < a[min]){
                min = j; continue;
            }
            if (a[j] > a[max]){
                max = j; 
            }
        }
        if (min != i){
            tmp = a[min];
            a[min] = a[i];
            a[i] = tmp;
        }
        if (max != i){
            tmp = a[max];
            a[max] = a[n - i - 1];
            a[n - i - 1] = tmp;
        }
    }
    return;    
}

//堆排序
void PercDown(int a[], int i, int n)
{
    int tmp = 0;
    int child = 2 * i;
    for (tmp = a[i]; 2 * i + 1 < n; i = child){
        child = 2 * i;
        if (child != n - 1 && a[child + 1] > a[child]){
            ++child;
        }
        if (tmp < a[child]){
            a[i] = a[child];    
        }
        else {
            break;
        }
    }
    a[i] = tmp;
    return;
}

void HeapSort(int a[], int n)
{
    int tmp = 0;
    for (int i = n / 2; i >= 0; --i){
        PercDown(a, i, n);
    }
    for (int i = n - 1; i > 0; --i){
        tmp = a[0];
        a[0] = a[i];
        a[i] = tmp;
        PercDown(a, 0, i);
    }
    return;
}

//归并排序
void Merge(int a[], int t[], int i, int m, int n)
{
    int pos = i;
    int j = m + 1;
    int length = n - i + 1;
    int start = i;
    while (i <= m && j <= n){
        if (a[i] <= a[j]){
            t[pos++] = a[i++];
        } else {
            t[pos++] = a[j++];
        }
    }
    while(i <= m){
        t[pos++] = a[i++];
    }
    while(j <= n){
        t[pos++] = a[j++];
    }
    memcpy(&a[start], &t[start], length * sizeof(int));
    return;
}

void MSort(int a[], int t[], int i, int n)
{
    if (i < n){
        int m = (i + n) / 2;
        MSort(a, t, i, m);
        MSort(a, t, m + 1, n);
        Merge(a, t, i, m, n);
    }
    return;
}

void MergeSort(int a[], int n)
{
    int *t = new int[n];
    if (NULL != t){
        MSort(a, t, 0, n - 1);
        print(t, n);
        delete []t;
    } else {
        cout<<"malloc error!"<<endl;
    }
    return;
}

//快速排序
void Swap(int *a, int *b)
{
    int tmp = 0;
    tmp  = *a;
    *a = *b;
    *b = tmp;
    return;
}

int Median3(int a[], int left, int right)
{
    int center = (left + right) / 2;
    if (a[left] > a[center]){
        Swap(&a[left], &a[center]);
    }
    if (a[left] > a[right]){
        Swap(&a[left], &a[right]);
    }
    if (a[center] > a[right]){
        Swap(&a[center], &a[right]);
    }
    Swap(&a[center], &a[right - 1]);
    return a[right - 1];
}

void Qsort(int a[], int left, int right)
{
    int i, j;
    int pivot;
    if (left + 3 <= right){
        pivot = Median3(a, left, right);    
        i = left;
        j = right - 1;
        for (;;){
            while(a[++i] < pivot){}
            while(a[--j] > pivot){}
            if (i < j){
                Swap(&a[i], &a[j]);
            } else {
                break;
            }
        }
        Swap(&a[i], &a[right - 1]);
        Qsort(a, left, i -1);
        Qsort(a, i + 1, right);
    } else {
        InsertSort(a + left, right - left + 1);
    }
    return;
}

int main()
{
    int a[9] = {34, 18, 12, 4, 1, 99, 178, 9, 37};
    //InsertSort1(a, 9);
    //ShellSort(a, 9);
    //TwoSelectSort(a, 9);
    //HeapSort(a, 9);
    //MergeSort(a, 9);
    Qsort(a, 0, 8);
    print(a, 9);
    return 0;
}