user input character evaluation to constant character

Question

I am trying to complete my guessing game here but the program would just crash when the user has input the correct number
I intended to use strcmpi function to evaluate the user's choice but it seems not working. The way that I am doing is to use c=getchar() be compared with 'y' or 'n' directly. Somehow I get a bad feeling about it.
So if this is not the proper way to do it please tell me what is the correct approach.
Also I get a warning says that

implicit declaration of function 'strcmpi

as I build it. Then I did try to add #include <string.h> and it pops out more errors indicating me that for example

warning: passing argument 1 of 'strcmpi' makes pointer from integer without a cast [enabled by default]|
note: expected 'const char *' but argument is of type 'char'

Any help would be appreciated and here is my program code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#define MAX_NUMBER 100

int main(void) {
int randNum;
srand((int)time(0));
randNum = rand() % 100 + 1;

long guessNum;
int count = 0;

do {
    printf("\nplz enter a guess from integer 1 to 100: %d", randNum);
    scanf("%ld", &guessNum);

    if(scanf("%ld", &guessNum)==1)
        {

    if (guessNum < randNum && guessNum >= 1) {
        printf("your guess is lower than the selected number");
        count++;
        printf("\nyou have %d times left to try", 100 - count);
    }
    if (guessNum > randNum && guessNum <= 100) {
        printf("your guess is higher than the selected number");
        count++;
        printf("\nyou have %d times left to try", 100 - count);
    }
    if (guessNum < 1 || guessNum > 100) {
        printf("your guess is out of the range, plz pick between 1-100");
        count++;
        printf("\nyou have %d times left to try", 100 - count);
    }
    if (guessNum == randNum) {
            count++;
        printf("congrats you got the right answer, you used %d times to make the right     guess", count
               );

        printf("\nwould you like to have another round? (y/n)\n");

        char c;
        c = getchar();


        if(strcmpi(c, 'y') == 0)
            {
                count = 0;
            printf("plz enter an integer from 1 - 100: ");
            scanf("%ld", &guessNum);
            }
            else if(strcmpi(c, 'n') == 0)
                {
                    printf("the game is ended!");
            break;
                    }else
                    {
                     printf("plz enter either y or n!");
                        }

            }

            }
            else
            {
            printf("plz enter a valid integer from 1 - 100: \n");
            char c;
            while((c = getchar())!= '\n');
            count++;
            printf("\nyou have %d times left to try", 100 - count);
            }
            } while (count < MAX_NUMBER);
            printf("\nthe guess time is used out!");

            return 0;
            }

Answer 1

strcmpi() operates on strings of characters, but getchar() retrieves only a single character.

You either need to do something like this:

// make a string for comparison
char s[2]={0};
s[0]=getchar();
if (strcmpi(s, "y")==0)
{
 //etc
}

or this:

// compare single character
char c=0;
c=getchar();
if (c=='y')
{
 // etc
}