7.3 快速排序的隨機化版本

已耗用時間為nlgn

 

#include <cstdlib>#include <iostream>#include <vector>#include <time.h>using namespace std;void input_v(vector<int> &v){     int data;     while(cin>>data)     {      v.push_back(data);     }}void print_v(const vector<int> &v){     for(vector<int>::const_iterator iter=v.begin();iter!=v.end();++iter)     cout<<*iter<<" ";     cout<<endl;}int partition(vector<int> &v,int s,int e)              //每次都隨機播放一個元素，並和最後一個元素交換{    srand((unsigned int)time(NULL));    int p=rand()%(e-s+1)+s;    int temp=v[p];    v[p]=v[e];    v[e]=temp;    int insert_u=s-1;    for(int i=s;i<e;++i)    {     if(v[i]<v[e])     {      int temp=v[++insert_u];      v[insert_u]=v[i];      v[i]=temp;     }    }    temp=v[e];    v[e]=v[++insert_u];    v[insert_u]=temp;    return insert_u;}void p_sort(vector<int> &v,int s,int e){     if(s<e)     {      int p=partition(v,s,e);      p_sort(v,s,p-1);      p_sort(v,p+1,e);     }}int main(int argc, char *argv[]){    vector<int> v;    input_v(v);    p_sort(v,0,v.size()-1);    print_v(v);    system("PAUSE");    return EXIT_SUCCESS;}