Guess Number Higher or Lower in C++

Suppose we are playing the Guess Game. The properties of this game is as follows −

Player 1 will pick a number from 1 to n. player2 have to guess which number I picked. Every time player2 guess wrong, player1 will tell player2 whether the number is higher or lower.

We can use the function guess(num) which will return 3 possible results as follows −

• -1 − Player1's number is lower

• 1 − Player1's number is higher

• 0 − Number is matched

So, if the input is like n = 10, pick = 5, then the output will be 5.

To solve this, we will follow these steps −

• l := 1,r := n

• while l −= r, do −

  • m := l+(r - l)/2

  • if guess(m) is the same as 0, then −

    • return m

  • if guess(m) is the same as -1, then −

    • r := m - 1

  • Otherwise

    • l := m + 1

• return 0

Example 

Let us see the following implementation to get a better understanding −

 Live Demo

#include <bits/stdc++.h>
using namespace std;
class Solution {
private:
   int number;
   int guess(int num){
      if(number > num)
         return 1;
      if(number < num)
         return -1;
      return 0;
   }
public:
   Solution(int n){
      number = n;
   }
   int guessNumber(int n) {
      int l=1,r=n,m;
      while(l<=r){
         m=l+(r-l)/2;
         if(guess(m)==0)
            return m;
         if(guess(m)==-1)
            r=m-1;
         else
            l=m+1;
      }
      return 0;
   }
};
main(){
   Solution ob(5); //pick = 5
   cout << (ob.guessNumber(10));
}

Input

5,10

Output

5