thanks a lot for opening the question. can anyone find out the logic error for m

ID: 3857547 • Letter: T

Question

thanks a lot for opening the question.

can anyone find out the logic error for me?

this is in C

#include<stdio.h>
#include<math.h>
#include<stdbool.h>
#include<ctype.h>
#include<stdlib.h>

void flushStdin();
int getmid(int low,int high);

int main(){

int usernum=0;
char userChar=' ';
int low=0;
int high=0;
int mid=0;
int lastGuess=0;

bool iamright=false;
bool absurd=false;
bool isvalidchar=true;
int i=1;

printf("Enter n: ");
scanf("%d",&usernum);
if((scanf("%d",&usernum))!=1)
{
printf("Error: invalid input. ");
return 0;
}

if(usernum<=0) {
     printf("Error: %d must be positive. ",usernum);
     return 0;
}
else{
high=usernum;
      low=getmid(low,high);
       printf("Is your number %d? ",low);
       lastGuess=low;

       for(i=1;!iamright&&!absurd&&isvalidchar;){//forloop
if(userChar!='l'&&userChar!='s'&&userChar!='e'){
      isvalidchar=false;
}
        else {userChar=getchar();
         flushStdin();
          userChar=tolower(userChar);


   switch(userChar){
        case'l':
        if((high-1)==low){
        absurd=true;
        }
        else{low=lastGuess;
        mid=getmid(low,high);
        lastGuess=mid;
        printf("Is your number %d?",mid);
        ++i;
        break;
        }

        case 's':
        if((low+1)==high){
        absurd=true;
        }
        else{high=lastGuess;
        mid=(getmid(low,high));
        lastGuess=mid;
        printf("Is your number %d?",mid);
        ++i;}
        break;

        case 'e':
        iamright=true;
        break;
}
}
}
}

if(iamright){
    printf("Your number must be %d. I used %d guesses.",mid,i);
}
if(absurd){
    printf("Error: that’s not possible. ");
}
if(!isvalidchar){
              printf("Error: invalid input. ");
           }

return 0;
}

void flushStdin(){
    char c;
    while ((c=getchar())!=EOF&&c!=' ')
    {

    }
}

int getmid(int low,int high){
return floor((double)(low+high)/2);
}

Explanation / Answer