快速排序 算法摘记

详细见算法导论，直接上实现；

最坏情况运行时间O(n*n)  ,平均/期望运行时间O(nlgn)

/*快速排序 参考算法导论 qucikSort 数组的关系坐标都要减1 */#include<iostream>#include<stdio.h>using namespace std;int len;void swap(int A[],int a,int b){int temp=A[a];A[a]=A[b];A[b]=temp;} int partition(int A[],int p,int r){int x,i,j;x=A[r];i=p-1;for(j=p;j<=r-1;j++){if(A[j]<=x){i++;swap(A,i,j);}}swap(A,i+1,r);return i+1;}void quickSort(int A[],int p,int r){int q;if(p<r){q=partition(A,p,r);quickSort(A,p,q-1);quickSort(A,q+1,r);}} int main(){int A[100];    while(scanf("%d",&len))    {        int i;        for(i=1;i<=len;i++)            cin>>A[i];        quickSort(A,1,len);        for(i=1;i<=len;i++)            cout<<A[i]<<" ";        cout<<endl;    }return 0;}

void Swap(ElementType *left, ElementType *right)    {        ElementType temp = *left;        *left = *right;        *right = temp;    }        int Partition(ElementType A[], int low, int high)    {        ElementType pivotkey = A[low];            while(low < high){            while(low < high && A[high] >= pivotkey)                  high--;            Swap(&A[low], &A[high]);                while(low < high && A[low] <= pivotkey)                low++;            Swap(&A[low], &A[high]);        }            return low;    }        void QSort(ElementType A[], int low, int high)    {        int pivotloc;            if(low < high){            pivotloc = Partition(A, low, high);             QSort(A, low, pivotloc - 1);            QSort(A, pivotloc + 1, high);        }    }        void QuickSort(ElementType A[], int low, int high)    {        QSort(A, low, high);    }