编辑代码

#include<iostream>
using namespace std;
int a(int searchKey,int array[],int arrLen) //第一个值等于 
{
   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;
}
int b(int searchKey,int array[],int arrLen) //最后一个值等于 
{
    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;
}
int c(int searchKey,int array[],int arrLen) //第一个值大于等于 
{
    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;
}
int d(int searchKey,int array[],int arrLen) //最后一个值大于等于 
{
    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;
}
void printArray(int array[],int arrLen) //输出 
{
    for (int i=0;i<arrLen;++i)
	{
        cout<<array[i]<< " ";
    }
    cout << endl;
}
int main()
{
	int arr[]={1,2,2,3,3,5,6,9};
	int arrayLen=sizeof(arr)/sizeof(int); 
	printArray(arr,arrayLen);
	cout<<"第一个2的位置："<<a(2,arr,arrayLen)<<endl;
	cout<<"最后一个2的位置："<<b(2,arr,arrayLen)<<endl;
	cout<<"第一个大于等于4的位置："<<c(4,arr,arrayLen)<<endl;
	cout<<"最后一个小于等于4的位置："<<d(4,arr,arrayLen)<<endl;
	return 0;
}