C语言编程中实现二分查找的简单入门实例

#include <stdio.h>
int binsearch(int x, int v[], int n);
main()
{
  int i, result, n;
 int wait;
  
  int x = 17; // 需要查找的数值
 int v[19]; // 定义一个数组
 // 给数组赋值
 for(i = 0; i < 20; ++i)
   v[i] = i;
 /**
 for(i = 0; i < 20; ++i)
 printf("%d \n", v[i]);
 */
 n = 20;
 result = binsearch(x, v, n);
 printf("%d", result);
 scanf("%d", &wait);
}
int binsearch(int x, int v[], int n)
{
 int low, high, mid;
 low = 0;
 high = n - 1;
 while (low <= high)
 {
 mid = (low + high) / 2;
 if(x < v[mid])
  high = mid - 1;
 else if (x > v[mid])
  low = mid + 1;
 else
  return mid;
 // 看看循环执行了多少次
 printf("mid = %d, low = %d, high = %d \n", mid, low, high);
 }
 return -1;
}

int find2(int *array,int n,int val) 
{ 
  if (n<=0) 
  { 
    return -1; 
  } 
 
  int begin=0,end=n-1,mid; 
  while(begin<=end)       
  { 
    mid=(begin+end)/2; 
    if (array[mid]==val) 
      return mid; 
    else if(array[mid]>val) 
      end=mid-1; 
    else 
      begin=mid+1; 
  } 
 
  return -1; 
} 

//二叉查找树数据结构 
typedef struct Btree 
{ 
  int data; 
  Btree *left; 
  Btree *right; 
}*PBTree; 
 
//创建二叉查找树，返回树的根节点 
PBTree CreateBTree(int *array,int n) 
{ 
  PBTree root=new Btree; 
  root->data=array[0]; 
  root->left=NULL; 
  root->right=NULL; 
 
  PBTree current,back,pNew; 
  for (int i=1;i<n;i++) 
  { 
    pNew=new Btree; 
    pNew->data=array[i]; 
    pNew->left=pNew->right=NULL; 
    current=root; 
    while(current!=NULL)  //找到合适的插入位置 
    { 
      back=current; 
      if(current->data>array[i]) 
        current=current->left; 
      else 
        current=current->right; 
    } 
    if(back->data>array[i]) 
      back->left=pNew; 
    else 
      back->right=pNew; 
  } 
 
  return root; 
} 
 
//利用二叉查找树进行递归查找 
bool find3(PBTree root,int val) 
{ 
  if (root==NULL) 
    return false; 
  if (root->data==val) 
    return true; 
  else if(root->data>val) 
    return find3(root->left,val); 
  else 
    return find3(root->right,val); 
}