I'm making a simple program that returns the sum of the sizes of user input.
User first inputs an int for amount of sizeof() sums to add
Followed by an input and char for data type.
This all works, BUT, what fails is if user types in anything other than 'c', 'd' or 'i' loop breaks and prints "invalid tracking code type."
My program fails on the conditional - even though the scanf() correctly obtains the char, it still fails.
FOR EXAMPLE:
INPUT:
3
10 i
7 c
12 d
OUTPUT
143 bytes
INPUT
1
1 o
OUTPUT
invalid tracking code type
how can you compare a user input using scanf in a loop?
#include <stdio.h>
int main()
{
int num, input, i, sum;
int invalid = 1;
sum = 0;
i = 0;
char type;
printf("give me a num!\n");
scanf("%d", &num);
while(i < num)
{
printf("int and char?\n");
//scanf("%d", &input);
//scanf(" %c\n", &type);
if (scanf("%d %c", &input, &type) != 2)
{
printf("TYPE IS: %c\n", type);
}
printf("TYPE IS: %c\n", type);
if(type != 'c' || type != 'd' || type != 'i')
{
printf("invalid tracking code type");
invalid = 0;
break;
}
i++;
//printf("what is i? %d\n", i);
sum = (sizeof(input)) + sum;
printf("IT's the sum %d\n", sum);
}
if(invalid != 0)
{
printf("%d bytes", sum);
}
return 0;
}
There are a number of other posts that answer similar issues, but wasn't able to find anything specifically for this issue.
I've tried a number of things such as separating the scanf(), using different types of operators for the conditional. It works fine without the conditional, but with the conditional it always returns "invalid tracking code type" even when they are correct.
Replace
if(type != 'c' || type != 'd' || type != 'i')
By
if(type != 'c' && type != 'd' && type != 'i')
Related
I'm writing a code that must identify the letter 't' or 'T' in a word, before or after the middle of it.
If the first half of the word does contain a 't' or a 'T', the program should output a 1. If the first half does not contain the letter 't' or 'T', but the second half does, then the program should output a 2. Otherwise, if there is no 't' or 'T' in the word at all, the program's output should be -1. The word entered will not have more than 50 letters.
#include <stdio.h>
#include <string.h>
int main() {
char word[50];
int i = 0, length, t = 0, T = 0;
scanf("%s", word);
length = strlen(word);
t = word[i] == 't';
T = word[i] == 'T';
while(!t || !T) {
if((t || T) && i <= length / 2) {
printf("%d", '1');
} else if((t || T) && i > length / 2) {
printf("%d", '2');
//}else{
// printf("%d", '-1');
}
i++;
}
return 0;
}
If I enter any word and press enter, nothing is printed. Another thing is that when I remove the comment slashes from the two lines at the bottom, the program goes through an infinite loop.
Could someone please help?
This sounds like a school assignment, so I'll focus on advising/critiquing your code rather than giving a solution.
The first recommendation I have is to use a for loop instead of a while loop. A Rule of thumb in C is to only use a while loop when you actually don't have any idea how many things you need your program to look at.
You already have the length of the string, so set up your for loop to loop exactly once for each character.
Next you need to change how you are using printf. The %d format specifier is for printing integers, but you are passing it '1'. This is not an integer, it is the ascii representation of the symbol 1 (which is actually has the value 49, see the ascii table for more info)
You can either pass printf the value 1, or use the %c specifier, which expects ascii characters.
Better yet, just say printf("1");
That doesn't get you all the way there, but I think it lays the ground work so you can find the solution!
Condition !t || !T has no sense to be used as loop condition ...ask yourself how the loop will end ? you need just to check i is less than length
Second, the assignments t = word[i] == 't'; T = word[i] == 'T'; outside the loop have no sense ...you will be just pointing to the zero index of the string ...you should check all characters
third , the printf lines need to use %d
fourth , you appear not getting the purpose of the program printing inside loop will lead to printing many numbers and you just want to know if there is t or T you need to print single line.you may use variable int result=0; to hold the value you want and print it in the end ...of course you will need using break statement in the if((t || T) && i <= length / 2) and if((t || T) && i > length / 2) because no need for more searching
fifth, you should re-read , re-think , re-code the assignment before going bored and asking about it
sixth, there is a working version by modifying your code but you should try writing a good solution before looking at a solution as it better to solve your problems by yourself
#include <stdio.h>
#include <string.h>
int main() {
char word[50];
int i = 0, length, t = 0, T = 0;
scanf("%s", word);
length = strlen(word);
int result=0;
while( i<length) {
t = word[i] == 't';
T = word[i] == 'T';
if((t || T) && i <= length / 2) {
result=1;
break;
} else if((t || T) && i > length / 2) {
result=2;
break;
}else{
result=-1;
}
i++;
}
printf("%d",result);
return 0;
}
# include <stdio.h>
int main()
{
char name[20];
int age;
int siblings;
int childrens;
printf ("Hello my name is A.I, what is your name? \n");
scanf("%s", &name);
printf("how old are you : \n");
scanf("%d",&age);
printf("how many siblings you have: \n");
scanf("%d", &siblings);
printf("how many children you have: \n");
scanf("%d", &childrens);
printf("so your name is : %s \n", name);
printf("and your age is : %d \n", age);
printf("you have siblings : %d\n", siblings);
printf("so you have childrens : %d\n", childrens);
return 0;
}
I'm trying to create a program where the program guesses what kind of number the user has in mind. First it will ask the user for a minimum and maximum number, for example 1 and 10(the number I have in mind should be between 1 and 10 then).
Lets say I have the number 4 in mind and the program will output a number. I can type in L for low, H for high or G for good.
If I type in L, the program should generate a number lower than the guessed number, for H it should guess an higher number. If I input G, the program should stop and print out how many times it guessed.
I have added my code below, what am I missing?
#include <stdio.h>
#include <stdlib.h>
int main() {
int minNumber;
int maxNumber;
int counter;
printf("Give min and max: ");
scanf("%d %d", &minNumber, &maxNumber);
//printf("%d %d", minNumber, maxNumber);
int num_between_x_and_y = (rand() % (maxNumber - minNumber)) + minNumber;
char input[100];
do {
printf("is it %d? ", num_between_x_and_y);
scanf("%s", input);
if (input == 'L') {
counter++;
}
if (input == 'H') {
counter++;
}
} while (input != 'G');
printf("I guessed it in %d times!", counter);
return 0;
}
I do not see any "counter" variable initialization
int counter = 1;
I do not see the new random number regeneration in the cycle, it should be something like:
do {
printf("is it %d? ", num_between_x_and_y);
scanf("%s", input);
if (input[0] == 'L') {
counter++;
maxNumber = num_between_x_and_y;
}
if (input[0] == 'H') {
counter++;
minNumber = num_between_x_and_y;
}
num_between_x_and_y = (rand() % (maxNumber - minNumber)) + minNumber;
} while (input[0] != 'G');
You can't use == to compare strings (which are multiple bytes).
Either do if (input[0] == 'L') to just compare the first letter the user entered to a literal value, or if (strcmp(input,"L") == 0) to compare everything the user entered to the 1 character string literal (to use strcmp you will need to add #include <string.h>
Also your code is missing other things, like counter should be set to presumably set to zero before you use it. I assume you haven't finished your code yet because you can't get the user input part to work.
I am very new to C programming, trying to adjust going from Python to C where the I/O syntax is very different. I would like to ask the user to enter two integers, then return to the user the two integers they had entered followed by the two integers multiplied together. My code follows:
#include <stdio.h>
int main(void) {
int a,b,c;
printf("Enter a: \n");
scanf("%d", &a);
printf("Enter b: \n");
scanf("%d", &b);
c = a*b;
printf("a = %d, b = %d, a*b = %d", a,b,c);
return 0;
}
The program does not allow the user to input a value, but rather chooses its own seemingly random integer, and the multiplication is also not correct. My output is as follows:
Enter a:
Enter b:
a = 2665720, b = -2147319336, a*b = -76879552
Even if the problem is with your IDE not passing the input to your program, the observed behavior is because of a and b being uninitialized when you call printf, to avoid that you must verify that scanf succeeded reading the integer. Here I suggest a way of doing that, it might not be the best solution, but it takes care of inavlid input, looping until valid input is recieved.
You have to check for valid input since scanf wont initialize the passed parameters on invalid input, a better way to do that is with the fgets function in combination with strtol that way you can check the validity of the input data
#include <stdio.h>
#include <stdlib.h>
int main(void)
{
int a,b,c;
char string[32];
char *endptr;
int valid;
valid = 0;
while (valid == 0)
{
printf("Enter a: ");
if (fgets(string, sizeof string, stdin) == NULL)
return -1;
if (*string == '\n') /* invalid input */
{
printf("Invalid Input\n");
continue;
}
a = strtol(string, &endptr, 10);
if ((*endptr != '\0') && (*endptr != '\n')) /* invalid input */
{
printf("Invalid Input\n");
continue;
}
printf("Enter b: ");
if (fgets(string, sizeof string, stdin) == NULL)
return -1;
if (*string == '\n') /* invalid input */
{
printf("Invalid Input\n");
continue;
}
b = strtol(string, &endptr, 10);
if ((*endptr != '\0') && (*endptr != '\n')) /* invalid input */
{
printf("Invalid Input\n");
continue;
}
valid = 1;
}
c = a * b;
printf("a = %d, b = %d -> a * b = %d\n", a, b, c);
return 0;
}
the uninitialized values will contain garbage, explaining the behavior you are observing.
With your program if you type any invalid string scanf will fail and you will try to print uninitialized values, you should at least check that it matched the correct number of arguments, like this
if (scanf("%d", &value) != 1)
something is wrong and you should either restart the program or, abort it.
I am doing a lab for an intro programming class
I have to make sure that an integer is entered. I thought this would do it but when I put in a letter it repeats in an endless loop.
I found this solution in another post
int num;
char term;
if (scanf("%d%c", &num, &term) != 2 || term != '\n')
printf("failure\n");
else
printf("valid integer followed by enter key\n");
But im not sure what I did wrong. Why is it not working in my code?
#include <stdio.h>
int main(void)
{
int oneVar;
char term;
double numOne;
double numTwo;
double sum;
double dif;
double quo;
double mult;
int checker = 1;
do
{
printf("Please choose one of the following:\n""1) Add\n""2) Subtract\n""3) Divide\n""4) Multiply\n""5) Quit\n");
if (scanf("%d%c" , &oneVar ,&term) != 2 || term != '\n')
{
printf ("This is not valid input\n\n");
checker = 1;
}
else if (oneVar == 5)
{
printf("Thank you. Goodbye.\n");
checker = 0;
}
else if (oneVar != 1 && oneVar !=2 && oneVar != 3 && oneVar != 4)
{
printf("This is not a valid input\n\n");
checker = 1;
}
else
{
printf("Please enter the first number:\n");
if (scanf("%lf%c" , &numOne ,&term) != 2 || term != '\n')
{
printf ("This is not valid input\n\n");
checker = 1;
}
printf("Please enter the second number:\n");
if (scanf("%lf%c" , &numTwo ,&term) != 2 || term != '\n')
{
printf ("This is not valid input\n\n");
checker = 1;
}
else if (oneVar == 1)
{
sum = numOne + numTwo;
printf("The sum is: %.2lf\n" ,sum);
checker = 0;
}
else if (oneVar == 2)
{
dif = numOne - numTwo;
printf("The difference is: %.2lf\n" ,dif);
checker = 0;
}
else if (oneVar == 3)
{
quo = numOne / numTwo;
printf("The quotient is: %.2lf\n" ,quo);
checker = 0;
}
else if (oneVar == 4)
{
mult = numOne * numTwo;
printf("The product is: %.2lf\n" ,mult);
checker = 0;
}
else if (oneVar == 5)
{
printf("Thank you. Goodbye.\n");
checker = 0;
}
}
} while (checker == 1);
return(0);
}
My prof posted this Im not sure how it helps but I thought it might help someone
To make sure that a user-input number is an integer you can use the notion of casting. Casting is a way to tell C to treat a variable as if it were a variable of a different type.
so, if I have something like this:
double myDouble;
myDouble = 5.43;
printf ("%d", (int) myDouble);
It will tell C to print myDouble, but to treat it like an integer. Only the 5 will be printed and you won't get any type mismatch errors. You can use casting to check to see if an input number is an integer by comparing the input to the (int) cast of the number. Something like this should work:
if(inputNum == (int) inputNum)
You'll still get 1.0 and 2.0 passing as valid numbers, but that is ok for now.
Why complicate things?
char x = 0;
scanf("%c", &x);
if (x >= 0x41 && x <= 0x7A)
printf("you entered a letter");
In ASCII table, letters have values between 0x41 ("A") and 0x7A ("z").
So, you just need to check the ASCII value of the input. :)
Using the %c to "consume" the end of line is not a good solution. If the user enters say:
123 abc<newline>
num will be 123, but term will be the space character. If you enter a letter rather than a number, the scan will stop without consuming any of the characters, the next input call will return due to the already buffered line, and may still consume nothing. Your program loops continuously because every input statement is failing to consume the newline and returns immediately. The standard input functions wait for a complete line before returning, if the line is not read completely, input functions do not need to wait.
There are a number of solutions, many of which such as the one you used are flawed, the method below, forces the input buffer to be flushed up to and including the newline.
int check = scanf( "%d", &num ) ;
while( getchar() != '\n' )
{
// do nothing
}
if( check != 2 )
printf("failure\n");
else
printf("valid integer followed by enter key\n");
If you use the %c format specifier at the end of the input, then a slightly different flush is necessary since the character input may be a newline:
int check = scanf( "%c", &ch ) ;
while( ch != '\n' && getchar() != '\n' )
{
// do nothing
}
My task is:
Write a program that reads input up to # and reports the number of times that the sequence ei occurs.
I wrote something that in most of the times works, but there are inputs when it dosent...
Like this input:(suppose to return 1)
sdlksldksdlskd
sdlsklsdks
sldklsdkeisldksdlk
#
number of combination is: 0
This is the code:
int main(void)
{
int index = 0;
int combinationTimes = 0;
int total = 0;
char userInput;
char wordChar[index];
printf("please enter your input:\n");
while ((userInput = getchar()) != '#')
{
if (userInput == '\n')
continue;
wordChar[index] = userInput;
index++;
total++;
}
for (index = 1; index < total; index++)
{
if (wordChar[index] == 'i')
{
if (wordChar[--index] == 'e')
{
combinationTimes++;
++index;
}
}
}
printf("number of combination is: %d", combinationTimes);
return 0;
}
Can you please tell me what am I not getting 1 using this input?
in the book he said to test it with "Receive your eieio award" and it worked...but after i played with it a little i see that not always.
It really doesn't seem necessary to read the file into an array. You just need to keep track of how many times ei is found before you read a # or reach EOF:
#include <stdio.h>
int main(void)
{
int c;
int ei_count = 0;
while ((c = getchar()) != EOF && c != '#')
{
if (c == 'e')
{
int c1 = getchar();
if (c1 == 'i')
ei_count++;
else if (c1 != EOF)
ungetc(c1, stdin);
}
}
printf("ei appeared %d times\n", ei_count);
return(0);
}
Testing (the program is called ei and is built from ei.c):
$ ei < ei.c
ei appeared 0 times
$ sed 1d ei.c | ei
ei appeared 1 times
$ sed 's/#/#/' ei.c | ei
ei appeared 4 times
$
The first one stops at the #include line, the second stops at the # in the comparison, and the third reads the entire file. It also gives the correct output for the sample data.
Analysing the code
Your primary problem is that you do not allocate any space for the array. Change the dimension of the array from index to, say, 4096. That'll be big enough for your testing purposes (but really the program should pay attention to the array and not overflowing it — but then I don't think the array is necessary at all; see the code above).
The next primary problem is that despite its name, getchar() returns an int, not a char. It can return any valid character plus a distinct value, EOF. So it must return a value that's bigger than a char. (One of two things happens if you use char. If char is a signed type, some valid character — often ÿ, y-umlaut, U+00FF, LATIN SMALL LETTER Y WITH DIAERESIS — is also treated as EOF even though it is just a character. If char is an unsigned type, then no input matches EOF. Neither is correct behaviour.)
Fixing that is easy, but your code does not detect EOF. Always handle EOF; the data may be malformatted. That's a simple fix in the code.
A tertiary problem is that the printf() statement does not end with a newline; it should.
Your test condition here is odd:
if (wordChar[--index] == 'e')
{
combinationTimes++;
++index;
}
It's odd to use one pre-increment and one post-increment, but that's just a consistency issue.
Worse, though, is what happens when the character i appears in the input and is not preceded by e. Consider the line #include <stdio.h>: you start with index as 1; that is an i, so you decrement index, but wordChar[0] is not an e, so you don't increment it again, but the end of the loop does, so the loop checks index 1 again, and keeps on going around the loop testing that the i is i and # is not e for a long time.
There's no reason to decrement and then increment index; just use:
if (wordChar[index-1] == 'e')
combinationTimes++;
With those fixed, your code behaves. You trouble was largely that you were using an array that was not big enough (being size 0), and you were overwriting quasi-random memory with the data you were reading.
#include <stdio.h>
int main(void)
{
int index = 0;
int combinationTimes = 0;
int total = 0;
int userInput;
char wordChar[4096];
printf("please enter your input:\n");
while ((userInput = getchar()) != '#' && userInput != EOF)
{
if (userInput == '\n')
continue;
wordChar[index] = userInput;
index++;
total++;
}
printf("total: %d\n", total);
for (index = 1; index < total; index++)
{
if (wordChar[index] == 'i')
{
if (wordChar[index-1] == 'e')
combinationTimes++;
}
}
printf("number of combination is: %d\n", combinationTimes);
return 0;
}
Note that you could reasonably write the nested if as:
if (wordChar[index] == 'i' && wordChar[index-1] == 'e')
combinationTimes++;
change your wordChar array value.
int main(void)
{
int index = 0;
int combinationTimes = 0;
int total = 0;
char userInput;
//char wordChar[index]; // index = 0
char wordChar[255]; // should change the value of array.
printf("please enter your input:\n");
while ((userInput = getchar()) != '#')
{
if (userInput == '\n')
continue;
wordChar[index] = userInput;
index++;
total++;
}
for (index = 1; index < total; index++)
{
if (wordChar[index] == 'i')
{
if (wordChar[--index] == 'e')
{
combinationTimes++;
++index;
}
}
}
printf("number of combination is: %d", combinationTimes);
return 0;
}
or maybe you can use pointer and then use malloc and realloc.