Question

I need to modify the code below to perform a binary search instead of a linear search.

#include <iostream>
using namespace std;

int searchList(int[], int, int);

int main()
{
   const int NUMS = 10;
   int Picks[NUMS] = { 13579, 26791, 26792, 33445, 55555,
                       62483, 77777, 79422, 85647, 93121 };

   int WinNums,
       Search;  

   cout << "Enter this week's winning five-digit number: ";
   cin >> WinNums;

   Search = searchList(Picks, NUMS, WinNums);

   if (Search == -1)
       cout << "Sorry, no winning ticket this week.\n";
   else
   {
       cout << "Congratulations!\nYou have the winning five-digit number: "
           << Picks[Search] << endl;
   }

   system("pause");

   return 0;
}

int searchList(int list[], int size, int value)
{
   int index = 0;
   int position = -1;
   bool found = false;

   while (index < size && !found)
   {
       if (list[index] == value)
       {
           position = index;
           found = true;
       }
       index++;
   }
   return position;
}

Answer 1

#include <iostream>

#include <algorithm>

using namespace std;

int binarySearchList(int[], int, int);

int main()

{

const int NUMS = 10;

int Picks[NUMS] = { 13579, 26791, 26792, 33445, 55555,

62483, 77777, 79422, 85647, 93121 };

int WinNums,

Search;

cout << "Enter this week's winning five-digit number: ";

cin >> WinNums;

Search = binarySearchList(Picks, NUMS, WinNums);

if (Search == -1)

cout << "Sorry, no winning ticket this week.\n";

else

{

cout << "Congratulations!\nYou have the winning five-digit number: "

<< Picks[Search] << endl;

}

system("pause");

return 0;

}

int binarySearchList(int list[], int size, int value)

{

int index = 0;

int position = -1;

int low = 0, high = size-1;

sort(list, list+size);

while (low <= high)

{

int mid = low + (high-low)/2;

if (list[mid] == value)

return mid;

if (list[mid] < value)

low = mid + 1;

else

high = mid - 1;

}

return -1;

}


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SEE OUTPUT


Thanks, PLEASE COMMENT if there is any concern.