C++二分查找算法实例

本文实例为大家分享C++二分查找算法，通过改变边界位置来进行查找的方法，代码如下：

#include <iostream>

using namespace std;

int search(int *p,int length,int key);
int search1(int *p,int length,int key);

int main()
{
 cout << "Hello world!" << endl;
 int a[] = {1,2,3,4,5,6,7,8,8,8,9,10,11,12,13,14};
 int len = sizeof(a)/sizeof(int);
 int pos = search1(a,len,8);
 cout << pos << endl;
 return 0;
}

int search1(int *p,int length,int key)
{
 int left=0;
 int right=length-1;
 while(left<=right)
 {
   int mid = (left+right)/2;
   if(p[mid]>=key)
   {
     right = mid-1;
   }else
   {
     left = mid+1;
   }
 }
 if(left<length && p[left]==key)
   return left;
 return -1;
}

int search(int *p,int length,int key)
{
 int left=0;
 int right = length -1;

while(left<=right)
 {
   int mid = (left+right)/2;
   if(p[mid]==key)
   {
     return mid;
   }
   if(p[mid] > key)
   {
     right = mid+1;
   }
   if(p[mid]<key)
   {
     left=mid-1;
   }
 }
 return -1;
}

来源：http://www.cnblogs.com/lucy-lizhi/p/7381306.html