青岛实习代码（2）

二分查找递归算法

#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
#define MAXL 10000

int a[MAXL],key;
int BinarySearch(int low,int high)
{
     if(low>high)
     return -1;

     int mid=(low+high)/2;
     if(key==a[mid])
         return mid;
     else if(key>a[mid])
         return BinarySearch(mid+1,high);
     else
         return BinarySearch(low,mid-1);
}
int main()
{
    int i,N;
    int f;
    cin>>N;
    for(i=0; i<N; i++)
    cin>>a[i];
    cin>>key;
    f=BinarySearch(0,N-1);
    if(f==-1)
        cout<<"no search!"<<endl;
    else
        cout<<f<<endl;
   return 0;
}

二分查找非递归算法

#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
#define MAXL 10000

int BinarySearch(int a[],int n,int key)
{
   int low=0,high=n-1;
   int mid;
   while(low<=high)
   {
     mid=(low+high)/2;
     if(key==a[mid])
         return mid;
     else if(key>a[mid])
         low=mid+1;
     else
         high=mid-1;
   }
   return -1;
}
int main()
{
    int a[MAXL],i,key,N;
    int f;
    cin>>N;
    for(i=0; i<N; i++)
    cin>>a[i];
    cin>>key;
    f=BinarySearch(a,N,key);
    if(f==-1)
        cout<<"no search!"<<endl;
    else
        cout<<f<<endl;
   return 0;
}

手写快速排序

#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
#define MAXL 10000

int a[MAXL],n;
void QuickSort(int low,int high)
{
    if(low<high)
    {
        int x,l,h;
        l=low,h=high;
        x=a[low];
        while(low<high)
        {
            while(low<high&&a[high]>=x)  --high;
            a[low]=a[high];
            while(low<high&&a[low]<=x) ++low;
            a[high]=a[low];
        }
        a[low]=x;
        QuickSort(l,low-1);
        QuickSort(low+1,h);
    }
}

void show()
{
    int i;
    for(i=0; i<n; i++)
        cout<<a[i]<<" ";
    cout<<endl;
}
int main()
{
    int i;
    cin>>n;
    for(i=0; i<n; i++)
        cin>>a[i];
    QuickSort(0,n-1);
    show();
    return 0;
}