Guessing Game

Hello world!

I need some help on this topic: Write a program that plays a simple number-guessing with its user. The user thinks of a number and then answers a series of questions asked by the computer until it correctly guesses the number.
Think of a number in the range of 1-50 and I’ll guess it.

Output of supposed program:
Is the number 25 ? no <ENTER>
Is the number less than 25 ? yes <ENTER>
Is the number 12 ? no <ENTER>
Is the number less than 12 ? yes <ENTER>
Is the number 6 ? no <ENTER>
Is the number less than 6 ? yes <ENTER>
Is the number 9 ? no <ENTER>
Is the number less than 9 ? no <ENTER>
Is the number 10 ? yes <ENTER>
I have succeeded in guessing your number!


I need to do this for numbers in the 1-200 range.
Here is the code I have so far:

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/* File: guess.c
 * --------------
 * This program is a guessing game.
 */
 
#include <cstdio>
#include "genlib.h"
#include "simpio.h"
#include "strlib.h"

int main(void)
{
	int usernum,high=200,low=0,myguess=100;
	string y_o_n;
	
	printf("This program is a guessing game!\n");
	while(true)
	{
		printf("Enter a number between 1-200.  ");
		usernum=GetInteger();
		if(usernum>0&&usernum<201)
		{
			break;
		}
		printf("Retry.\n");
	}
	while(true)
	{
		printf("Is the number %d (yes/no)?  ",myguess);
		y_o_n=GetLine();
		if(StringEqual(y_o_n,"no")==true)
		{
			printf("Is the number less than %d (yes/no)?  ",myguess);
			y_o_n=GetLine();
			if(StringEqual(y_o_n,"yes")==true)
			{
				myguess=myguess/2;
			}
			else
			{
				low=myguess*2;
				myguess=(myguess+high)/2;
			}
		}
		else
		{
			printf("I have succeeded in guessing your number!");
			getchar();
			return 0;
		}
	}
	getchar();
	return 0;
}


The highlighted pieces of code are where I need help.
Right now, the program output is:

This program is a guessing game!
Enter a number between 1-200.  127
Is the number 100 (yes/no)?  no
Is the number less than 100 (yes/no)?  no
Is the number 150 (yes/no)?  no
Is the number less than 150 (yes/no)?  yes
Is the number 75 (yes/no)?  no
Is the number less than 75 (yes/no)?  yes
Is the number 137 (yes/no)?  no
Is the number less than 137 (yes/no)?  yes
Is the number 68 (yes/no)?  no
Is the number less than 66 (yes/no)?  yes
Is the number 134 (yes/no)?  no
Is the number less than 134 (yes/no)?  yes
Is the number 67 (yes/no)?  no
Is the number less than 167 (yes/no)?  yes
Is the number 133 (yes/no)?  no
Is the number less than 133 (yes/no)?  yes
Is the number 66 (yes/no)?  no
Is the number less than 66 (yes/no)?  yes
Is the number 133 (yes/no)?  no
Is the number less than 133 (yes/no)?  yes
Is the number 66 (yes/no)?  no
Is the number less than 66 (yes/no)?  ...
...


As you can see, it gets stuck at 67-132 numbers. I need help on the bold parts because that is where the next guess is calculated. Obviously, I am missing some part of the process. I need a piece of algorithm for this process. From there, I can figure out what to do (I am a pretty fast learner...).

Any advice would be great!
Thank you,
~Usandfriends

P.S.: Sorry, this code is written in C. If you want it in C++ just ask.
Last edited on
I didn't look into it, but it looks like there is problem with logic.
Here is how I did this:
We will create two variables: high and low. high will be a maximum possible number (200 in your case) and low will be the lowest (1 in yor case)
Then the loop starts.
guess = (low + high) / 2
If guess lower than your number: low = guess + 1
If guess higher than your number: high = guess - 1
Start again.
Yes, but I need to do it in the least possible questions.
This is the most efficient dichotomy methos, which gives you result in least steps
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