quickSort

推荐慕课网，刘宇波老师《算法与数据结构》链接：http://coding.imooc.com/class/71.htmlquickSort 课堂笔记/* first */#include <cstdlib>#include <iostream>#include <ctime>using namespace std;template<typename T>int partition(T arr[],int l,int r){    swap(arr[l],arr[rand()%(r-l+1)+l]);    T v = arr[l];    int j = l;    for(int i = l+1;i <= r;i++){        if(arr[i] < v){            j++;            swap(arr[j],arr[i]);        }    }    swap(arr[l],arr[j]);    return j;}template<typename T>void _quickSort(T arr[],int l,int r){    if(l < r){        int p = partition(arr,l,r);        _quickSort(arr,l,p-1);        _quickSort(arr,p+1,r);    }}template<typename T>void quickSort(T arr[],int n){    srand(time(NULL));    _quickSort(arr,0,n-1);}int main(){    int arr[] = {9,8,7,6,5,4,3,2,1};    int n = sizeof(arr)/sizeof(arr[0]);    quickSort(arr,n);    for(int i = 0;i<n;i++)       printf("%d ",arr[i]);    printf("\n");    return 0;}/* 初步优化 */#include<iostream>#include<cstdlib> #include<ctime>using namespace std;template<typename T>int partition2(T arr[],int l,int r){    swap(arr[l],arr[rand()%(r-l+1)+l]);    T v = arr[l];    //arr[l+1...i) <= v ,arr[j...r] >= v    int i = l+1,j = r;    while(true){        while(i <= r && arr[i] < v) i++;        while(j >= l+1 && arr[j] > v) j--;        if(i > j) break;        swap(arr[i],arr[j]);        i++,j++;    }       swap(arr[l],arr[j]);    return j;}template<typename T>void _quickSort2(T arr[],int l,int r){    if(l < r){        int p = partition2(arr,l,r);        _quickSort2(arr,l,p-1);        _quickSort2(arr,p+1,r);    }}template<typename T>void quickSort2(T arr[],int n){    srand(time(NULL));    _quickSort2(arr,0,n-1);}int main(){    int arr[] = {9,8,7,6,5,4,3,2,1};    int n = sizeof(arr)/sizeof(arr[0]);    quickSort2(arr,n);    for(int i = 0;i<n;i++)       printf("%d ",arr[i]);    printf("\n");    return 0;}