编辑代码

#include<iostream>
using namespace std;




//查找第一个值等于给定值的元素
int binarySearchFirstEqual(int searchKey,int array[],int arrLen) 
{
   int low=0;
   int high=arrLen-1;
   int keyPos=-1;
   while(low<=high)
    {
        int mid=low+((high-low+1)>>1);
        if(array[mid]>searchKey)
		{
            high=mid-1;
        }
        else if(array[mid]<searchKey)
		{
            low=mid+1;
        }
        else
		{
            if(mid==0 || array[mid-1]!=searchKey)
			{
                keyPos=mid;
                break;
            }
            else
			{
                high=mid-1;
            }
        }
	}
   return keyPos;
}




//查找最后一个值等于给定值的元素 
int binarySearchLastEqual(int searchKey,int array[],int arrLen) 
{
    int low=0;
    int high=arrLen-1;
    int keyPos=-1;
    while(low<=high)
	{
    	int mid=low+((high-low+1)>>1);
        if(array[mid]>searchKey)
		{
            high=mid-1;
        }
        else if(array[mid]<searchKey)
		{
            low=mid+1;
        }
        else
		{
                 if(mid==arrLen-1 || array[mid+1]!=searchKey)
		        {
                     keyPos=mid;
                     break;
                 }
                 else
		        {
                     low=mid+1;
                 }
        }
    }
   return keyPos;
}





//查找第一个大于等于给定值的元素
int Larger(int searchKey,int array[],int arrLen) 

{
    int low=0;
    int high=arrLen-1;
    int keyPos=-1;
    while(low<=high)
	{
              int mid=low+((high-low+1)>>1);
              if(array[mid]>=searchKey)
            	{
                  if(mid==0 || array[mid-1]<searchKey)
            		{
                      keyPos=mid;
                      break;
                  }
                  else
            		{
                      high=mid-1;
                  }
              }
              else
            	{
                  low=mid+1;
              }
    }
   return keyPos;
}




//查找最后一个小于等于给定值的元素
int Smaller(int searchKey,int array[],int arrLen)
{
            int low=0;
            int high=arrLen-1;
            int keyPos=-1;
            while(low<=high)
            {
                int mid=low+((high-low+1)>>1);
                if(array[mid]<=searchKey)
            	{
                    if(mid==arrLen-1 || array[mid+1]>searchKey)
            		{
                        keyPos=mid;
                        break;
                    }
                    else
            		{
                        low=mid+1;
                    }
                }
                else
            	{
                    high=mid-1;
                }
            }
   return keyPos;
}




int main()
{
	int arr[]={1,2,3,4,5,6,7,8,9};
	
    int len=sizeof(arr)/sizeof(int); 
	
    cout<<"查找的数字:7"<<endl;
    cout<<"binarySearchFirstEqual下标："<<binarySearchFirstEqual(7,arr,len)<<endl;
	
    cout<<"binarySearchLastEqual下标："<<binarySearchLastEqual(7,arr,len)<<endl;
	
    cout<<"Larger下标:"<<Larger(7,arr,len)<<endl;
	
    cout<<"Smaller下标："<<Smaller(7,arr,len)<<endl;
}