二分查找

#include<stdio.h>

int BinaryFind(int *a,int n,int data)  //非递归实现
{
  if(a==NULL||n<=0)
     return -1;
  int begin=0;
  int end=n-1;
  while(begin<=end)
   {
     int mid=begin+(end-begin)/2;
     if(a[mid]==data)
        return mid;
     else if(a[mid]<data)
        begin=mid+1;
     else
        end=mid-1;
   }
  return -1;
}
int BinaryRecursive(int*a,int begin,int end,int data) //递归实现二分查找
{
   if(a==NULL||begin>end)
     return -1;
   int mid=begin+(end-begin)/2;
   if(a[mid]==data)
     return mid;
   else if(a[mid]<data)
      return BinaryRecursive(a,mid+1,end,data); //注意return
   else
      return  BinaryRecursive(a,begin,mid-1,data);

}

int main()
{
  int a[]={1,2,3,5,6,7};
  int n=sizeof(a)/sizeof(a[0]);
  for(int i=0;i<n;i++)
  {
    printf("%d\n",a[i]);
   }
  printf("4 is in the line: %d\n",BinaryFind(a,n,4));
  printf("5 is in the line:%d\n",BinaryRecursive(a,0,n-1,5));
  return 0;
}