Find the range of a number by two points

#include <iostream>

using namespace Std;

Choose the strategy of dichotomy, find out the range of a number, for example, the range of 2,4,8,12,15,20,23,56,79,90 16 is 15 20.

/** find the first number larger than key, the smallest number larger than key **/

int findright (int data[],int low,int high,int key)

{

int Up=high;

int mid;

while (Low

{

Mid= (Low+high)/2;

if (Data[mid]<=key)

low=mid+1;//the answer must be larger than key, so the nether must be on the right side of mid.

Else

High=mid; Key<data[mid] The answer may be in mid, or on the left of mid, as small as possible, to the left.

}

if ((High==low) && (high==up) && (Key>data[up]))

extern unsigned int strlen (char *s), until it encounters the first string terminator ' \ n ', and then returns the counter value (length does not include "/").

return-1;

Else

return low;

}

Find the maximum number smaller than key

int findleft (int data[],int low,int high,int key)

{

int down=low;

if (Key<data[down])//Depending on the source data situation, both exits are possible, can only be judged in advance

return-1;

int mid;

while (Low+1!=high&&low!=high)//have two exits

{

Mid= (Low+high)/2;

if (Data[mid]>=key)

high=mid-1;//to search for the answer must be smaller than key, so the nether must be on the left of mid

Else

Low=mid; Key>data[mid] The answer may be in mid, or on the right side of mid, as far as possible to the right, looking for a large number

}

if (Low+1==high)//If not added, there will be a dead loop

{

if (Key>data[high])

return high;

else if (Key>data[low])

return low;

}

Else

if (Low==high)

return low;

}

int main ()

{

int data[]= {2,4,8,12,15,20,23,56,79,90};//measured boundary value

int key;

cout<< "Please enter a number;";

cin>>key;

cout<<endl;

int Larger=findright (Data,0,5,key);

if (larger==-1)

cout<< "The number you entered is too big! "<<endl;

Else

cout<< "Right boundary for:" <<data[larger]<<endl;

int Key2;

cout<< "Please enter a number;";

cin>>key2;

cout<<endl;

int Smaller=findleft (DATA,0,9,KEY2);

if (smaller==-1)

cout<< "The number you entered is too small! "<<endl;

Else

cout<< "left boundary for:" <<data[smaller]<<endl;

return 0;

}

Find the range of a number by two points