二分法查找和快速排序

  1 #include<stdio.h>
  2 
  3 
  4 //快速排序
  5 void QuickSort(int * a,int left,int right)
  6 {
  7     if(left>right)
  8     {
  9         return;
 10     }
 11     int stand=a[left];
 12     int i=left;
 13     int j=right;
 14     //得到基准数位置
 15     while(i!=j)
 16     {
 17         while(i<j&&a[j]>=stand)
 18         {
 19             --j;
 20         }
 21         while(i<j&&a[i]<=stand)
 22         {
 23             ++i;
 24         }
 25         if(i<j)
 26         {
 27             int temp=a[i];
 28             a[i]=a[j];
 29             a[j]=temp;
 30         }
 31     }
 32     //将基准数放入找出的位置
 33     a[left]=a[i];
 34     a[i]=stand;
 35     //递归
 36     QuickSort(a,left,i-1);
 37     QuickSort(a,i+1,right);
 38     return;
 39 }
 40 
 41 
 42 //递归实现二分法查找
 43 int BinarySearch(int * a,int key,int low,int high)
 44 {
 45     if(low>high||key<a[low]||key>a[high])        //越界处理
 46     {
 47         return -1;
 48     }
 49     int middle=(low+high)/2;
 50     if(key==a[middle])
 51     {
 52         return middle;
 53     }
 54     if(middle==low||middle==high)
 55     {
 56         if(key==a[low])
 57         {
 58             return low;
 59         }
 60         if(key==a[high])
 61         {
 62             return high;
 63         }
 64         else
 65         {
 66             return -1;
 67         }
 68     }
 69     if(key<a[middle])
 70     {
 71         return BinarySearch(a,key,low,middle);
 72     }
 73     if(key>a[middle])
 74     {
 75         return BinarySearch(a,key,middle,high);
 76     }
 77 }
 78 
 79 //循环实现二分法查找
 80 int BinarySearchByCircle(int * a,int key,int high)
 81 {
 82     int low=0;
 83     int middle;
 84     while(high>=low)
 85     {
 86         middle=(high+low)/2;
 87         if(key==a[middle])
 88         {
 89             return middle;
 90         }
 91         if(key<a[middle])
 92         {
 93             high=middle-1;
 94         }
 95         if(key>a[middle])
 96         {
 97             low=middle+1;
 98         }
 99     }
100     return -1;
101 }
102 
103 int main()
104 {
105     int a[]={5,23,5,7,1};
106     printf("----------------快速排序--------------\n");
107     QuickSort(a,0,4);
108     for(int i=0;i<5;i++)
109     {
110         printf("%d\n",a[i]);
111     }
112     printf("\n---------------非递归二分法查找元素5的位置-----------------\n");
113     printf("%d\n",BinarySearchByCircle(a,5,4));
114     printf("\n---------------递归二分法查找元素5的位置------------------\n");
115     printf("%d\n",BinarySearch(a,5,0,4));
116     return 0;
117 }