All the cases work except the switch 'a' case. The a case runs the insert method below. Any help would be appreciated, thanks. printf statements inside the switch statement don't work.
void insert() {
char name;
printf("enter your name");
scanf("%c", &name);
for(int i = 0; i < LENGTH; i++){
if (!Thesame(names[1], name) == 0 && counter != LENGTH && strlen(name) <= MAX){
for(int j = 0; j < LENGTH; j++){
strcpy(names[counter],name);
}
}
else{
printf("error");
}
}
```
int main() {
while (1) {
char input;
printf("Type in 'a' be added to the system \n");
printf("Type in 'n' to print next patient and remove from
waitlist \n");
printf("Type in 'l' to list the patients on the waitlist \n");
printf("Type in 'q' to quit the program \n");
scanf("%c", &input);
switch (input) {
case 'a':
insert();
break;
case 'n':
next();
break;
case 'l':
print();
break;
case 'q':
return 0;
}
}
}
char name;: name can contain only a single character. So when you type for example: cuq, name will contain c, then insert does whatever with name and then returns to main. Then in main scanf("%c", &input) will read the remaining characters from the input buffer ('u' and 'q') and because of case 'q': the programs stops. Use a debugger or put some printfs at strategic places in your code to see what happens.
You want a string here and you probably want something like this in insert:
char name[100];
printf("enter your name: ");
scanf("%s", name);
...
You also probably need to change the Thesame function.
Related
I have a little problem with entering characters in C language. The program works fine after the first iteration of the loop, all the options from the MENU a), b), c), d), e) work. The problem, however, appears in subsequent iterations of the loop with the "a" and "c" options. It is as if it does not load characters immediately, only in the following lines. I put a link with an overview screen with the code and the console window.
Or maybe the problem is in another piece of code?
That's my fragment of code:
char menu(void) {
int ch;
printf("Enter the letter corresponding to the selected option:\n");
printf(" a) adding numbers to the BST tree from the keyboard \n");
printf(" b) adding random numbers to the tree to determine the number of numbers \n");
printf(" c) writing numbers in order from the smallest \n");
printf(" d) removing a specific number \n");
printf(" e) end \n");
while ((ch = getchar()) != EOF)
{
while (getchar() != '\n')
{
continue;
}
ch = tolower(ch);
if (strchr("abcde", ch) == NULL)
puts("Enter a, b, c, d or e:");
else
break;
}
if (ch == EOF)
ch = 'e';
return ch;
}
int main(int argc, char* argv[]) //This is main function
{
int number, size, size_moose, element_to_delete;
int left_compartment, right_compartment;
char choice;
root = NULL;
printf("Welcome to a number sorting program that uses the BST (Binary Search Tree) sorting algorithm\n");
printf("####################################################################################################\n");
printf("####################################################################################################\n");
printf("\t\tMENU\n\n");
while ((choice = menu()) != 'e') {
switch (choice) {
case 'a':
printf("How many numbers do you want to enter?\n");
scanf("%d", &size);
printf("Enter the numbers one after the other:\n");
for (int i = 0; i < size; i++)
{
scanf("%d", &number);
dodawanie(number, root); //the name of the adding function
}
printf("\n");
break;
case 'b':
printf("How many numbers do you want to draw?\n");
scanf("%d", &size_moose);
printf("Enter the left boundary of the range (e.g. 1):\n");
scanf("%d", &left_compartment);
printf("Enter the right bound of the range (e.g. 100):\n");
scanf("%d", &right_compartment);
for (int i = 0; i < size_moose; i++)
{
//using a random number function
number = losowanie(left_compartment, right_compartment);
dodawanie(number, root);
}
printf("...I drew a %d number/numbers...\n", size_moose);
printf("\n");
break;
case 'c':
printf("Listing the numbers in order from the smallest:\n");
in_order_tree_walk(root); //a function that prints out ordered numbers
printf("\n");
break;
case 'd':
printf("Give a specific value to delete:\n");
scanf("%d", &element_to_delete);
kasowanie(szukaj(root, element_to_delete)); //using a function to remove a specific element
printf("\n");
break;
default:
printf("Error in switch statement\n");
}
}
printf("####################################################################################################\n");
printf("####################################################################################################\n");
printf("Goodbye!\n");
return 0;
}
I put a screen with an example of the program's operation
problemC
I've attempted to find if the user has inputted a product id value that's a duplicate and if so, it just tells them that it's a duplicate value and then returns to the menu in my switch statement.
The actual result i get, is that after "productsfilled == 0", it won't utilise the For Loops to check for the duplicates and productsfilled will remain at 1. I've looked online and this way of finding duplicates tends to work and i have used it previously in my code, so I don't think that could be the issue.
Here's my code:
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
#include <ctype.h>
#include <conio.h>
int productsfilled;
struct ProductData{
int product_id;
char product_name[120];
int price;
};
int quiz_5(){
char ch;
int size, input = 0;
struct ProductData products[20];
while(1){
printf("\nWelcome To The Super Mall's Product List. Please Select An Option:\n1. Add Product\n2. Display Product\n3. Delete Product\n");
fflush(stdin);
switch(getchar()){
case '1':
printf("\nPlease Enter Product ID:");
scanf("%d",&products[productsfilled].product_id);
printf("\nPlease Enter Product Name:");
scanf("%s",&products[productsfilled].product_name);
printf("\nPlease Enter Product Price:");
scanf("%d",&products[productsfilled].price);
printf("Productsfilled: %d",productsfilled);
if(productsfilled == 0){
productsfilled = 1;
break;
}
for(int i = 0; i < productsfilled;i++){
for (int j = i + 1; j < productsfilled;j++){
if(products[i].product_id == products[j].product_id){
printf("\nPlease Use Different Product ID");
break;
}else{
printf("test");
productsfilled += 1;
break;
}
}
}
break;
case '2':
while(1){
for(int i = 0;i < productsfilled;i++){
printf("Product ID: %d Product Name: %s Product Price: %d\n",products[i].product_id,products[i].product_name,products[i].price);
}
printf("Please Press Enter To Continue");
fflush(stdin);
if(getchar() == '\n'){
break;
}
}
case '3':
break;
case '\n':
break;
default:
printf("Please Select An Option:\n1. Add Product\n2. Display Product\n3. Delete Product: ");
}
}
}
int main() {
int input = 1;
printf("Welcome to my assignment. Which quiz do you want to run (please input the number of the quiz e.g. for quiz 1, type 1): \n-Quiz 1\n-Quiz 2\n-Quiz 3\n-Quiz 4\n-Quiz 5\n-Quiz 6\n-Quiz 7\n");
while(input == 1){
fflush(stdin);
switch(getchar()){
case '5':
quiz_5();
break;
case '\n':
printf("Welcome to my assignment. Which quiz do you want to run (please input the number of the quiz e.g. for quiz 1, type 1): \n-Quiz 1\n-Quiz 2\n-Quiz 3\n-Quiz 4\n-Quiz 5\n-Quiz 6\n-Quiz 7\n");
getchar();
default:
printf("Invalid Input\n");
} }
return 0;
}
The problem is that you don't increment productsfilled before you enter the loop...therefore, productsfilled is always 1 less than the actual length of your array which means that you don't compare all elements in the array.
Try your program on 2 inputs, both with the same ID. You'll see that you don't compare anything.
You are wrong when using scanf for string input:
scanf("%s",&products[productsfilled].product_name);
You should not use &, you should use as below:
scanf("%119s",products[productsfilled].product_name);
OT, in main function:
switch(getchar()){
case '5':
...
Because getchar() will return int value, so if you want to access to quiz_5, you have to type 35 (ANSCI code) instead of type 5 when you run your program.
char a = '5';
similar to:
int a = 35;
I need to write a script for the user to enter a score between 0 and 10, flush the bad input out, if user inputs it and then using a switch statement, tell a user what grade did he/she got.
Here is my script:
...
int main()
{
int input; // input from user
printf("Enter the number between 0 and 10 and I will tell you your grade!");
while ((input=scanf("Your input:", &input) != EOF))
{
if (input < 0 || input > 10) //input is invalid
{
printf("Sorry, invalid character data.");
while (getchar() !='\n')
{
printf("Your input must be from 0 to 10.", input);
scanf("%d", &input); //This part looks very bad for me
}
}
else
switch (input)
{
case 0:
case 1:
case 2:
case 3:
case 4:
case 5:
printf("Your grade is F. \n");
break;
case 6:
printf("Your grade is D. \n");
break;
...
I got this far with my homework, and here are some "leftover" problems I can't fight with.
1) Whenever user submits anything after enter, it goes into infinite loop and prints Your grade is F., even when case = 6 for example.
2) I used break; at the end of each case. It looks like they don't work(?)
3) It looks like the problem in the second line in the second loop
scanf("%d", &input); //This part looks very bad for me
but then I guess the scripts accepts it as true since the else statements that includes switch begins to work, because otherwise it wouldn't print Your grade is F.
Try the following code. Have a look at what flush_stream is doing when we have invalid data...
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
void flush_stream();
void flush_stream() {
char c;
do {
c = getchar();
}
while (!isdigit(c) && c != '\n');
ungetc(c, stdin);
}
int main(void) {
const char *prompt = "Input please: ";
int input; // input from user
printf("Enter the number between 0 and 10 and I will tell you your grade!\n");
while(1) {
printf("%s", prompt);
int ret = scanf("%d", &input);
if(ret == 0) {
printf("Sorry, invalid character data, your input must be from 0 to 10.\n");
flush_stream();
continue;
}
if(ret > 0) {
if (input < 0 || input > 10) {
printf("Sorry, invalid character data, your input must be from 0 to 10.\n");
flush_stream();
continue;
}
switch (input) {
case 0:
case 1:
case 2:
case 3:
case 4:
case 5:
printf("Your grade is F. \n");
break;
case 6:
printf("Your grade is D. \n");
break;
}
}
}
}
It seems you are using scanf and printf wrong.
To input a number:
scanf("%d", &input);
To output a number:
printf("%d\n", input);
And in you while loop, when the input is illegal, why not just continue to the next loop?
while (true) {
printf("input your grade here: ");
if (scanf("%d", &input) == EOF) {
break;
}
if (input < 0 || input > 10) {
printf("your input is illegal.\n");
continue;
}
switch (input) {
...
}
}
I am implementing a polynomial using array. This is the Problem Statement:
Write a menu-driven program to represent Polynomials as a data structure using arrays. and write functions to add, subtract and multiply two polynomials; multiply a polynomial with a constant, find whether a polynomial is a "zero- polynomial, return the degree of the polynomial. Assume that a new polynomial is created after each operation. How would you input and output polynomials?
I have created the input and output functions. But my do while loop is running twice.. Help me finding out why.
The do-while loop
do{
print_menu();
scanf("%c",&ch);
printf("\nch = %c\n",ch);
switch(ch){
case '1':
create_poly(poly,termpool,&next_poly);
break;
case '2':
print_poly(poly,termpool,&next_poly);
break;
case 'q':
break;
default:
printf("Invalid choice.");
}
}while(ch != 'q');
return 0;
}
The print_menu() function
void print_menu()
{
printf("\n1. Create a new polynomial.");
printf("\n2. Print polynomial.");
printf("\nq. Exit");
printf("\nEnter Choice:");
}
The create_poly() function
void create_poly(int poly[][2], int termpool[][2], int *next_poly)
{
int beg = poly[*next_poly][0];
int end, size, i, j;
printf("Enter size of the polynomial:");
scanf("%d",&size);
poly[*next_poly][1] = beg + size - 1;
end = poly[*next_poly][1];
printf("Enter terms of the polynomial(coeff then exponent):\n");
for(i=beg; i<=end; i++){
for(j=0; j<2; j++){
scanf("%d ",&termpool[i][j]);
}
}
poly[++(*next_poly)][0] = end + 1;
}
The print_poly() function
void print_poly(int poly[][2],int termpool[][2],int *next_poly)
{
int pos,beg,end;
int i;
printf("Enter position of the polynomial:");
scanf("%d",&pos);
if(pos-1 > *next_poly){
printf("Invalid position.");
return;
}
beg = poly[pos-1][0];
end = poly[pos-1][1];
for(i=beg; i<=end; i++){
printf(" %dx^%d +",termpool[i][0],termpool[i][1]);
}
printf("\b = 0");
}
Here is a sample output:
1. Create a new polynomial.
2. Print polynomial.
q. Exit
Enter Choice:1
ch = 1
Enter size of the polynomial:2
Enter terms of the polynomial(coeff then exponent):
2 4
6 7
1. Create a new polynomial.
2. Print polynomial.
q. Exit
Enter Choice:
ch =
Invalid choice.
1. Create a new polynomial.
2. Print polynomial.
q. Exit
Enter Choice:q
ch = q
Tried flushing the stdin… The problem stays. Printing the value of ch in each step, I think it is a whitespace. Where does the white space comes?
The answer to abnormal behavior of scanf answers this question also.
If you test the next code you will note the same problem
int main() {
char c;
do {
scanf_s("%c", &c);
if (c != 'q')
printf("test scanf() function\n");
} while (c);
}
the scanf() function works when the enter key is pressed, but this insert another char in the buffer input, the char of new line '\n', it is taken again by scanf() because the loop block. Try to change the previous code by this code:`
do {
scanf_s("%c", &c); // or c = getchar();
switch (c){
case '\n':
break;
default:
printf("test scanf() function\n");
}
} while (c);`
and will work fine. In your code only add a new case in the switch block:
switch(ch) {
case '1':
create_poly(poly,termpool,&next_poly);
break;
case '2':
print_poly(poly,termpool,&next_poly);
break;
case '\n':
break;
case 'q':
break;
default:
printf("Invalid choice.");
}
sorry, English is not my native language
There's an extra character waiting to be consumed after you make your initial choice, that's why the loop is executing twice.
See this question on the comp.lang.c FAQ
I'm using a while, switch, case statement for my menu and when it runs it keeps saying enter choice, I know while(1) creates an infinite loop but is there a way to avoid this?
while(1)
{
printf("\nEnter Choice \n");
scanf("%d",&i);
switch(i)
{
case 1:
{
printf("Enter value to add to beginning: ");
scanf("%c",&value);
begin(value);
display();
break;
}
case 2:
{
printf("Enter value to add last: ");
scanf("%c",&value);
end(value);
display();
break;
}
case 3:
{
printf("Value to enter before\n");
scanf("%c",&loc);
printf("Enter value to add before\n");
scanf("%c",&value);
before(value,loc);
display();
break;
}
case 4 :
{
display();
break;
}
}
}
Any help would be appreciated.
While(1) is ok. But you have to have some conditions to finish the loop. Like :
while(1){
.........
if(i == 0)
break;
............
}
Add a space at the beginning of every "%d" and "%c",because scanf always leaves a newline characters in buffer:
"%d"->" %d"
"%c"->" %c"
Alternative solution,
int i = !SOME_VALUE;
while(i != SOME_VALUE)
{
printf("\n\nEnter Choice ");
scanf("%d",&i);
switch(i)
{
case SOME_VALUE: break;
.
.
.
// the rest of the switch cases
}
}
SOME_VALUE is any integer number notify to stop loop.
Alternatively, you may want to put a condition in the loop that relates to the input, e.g.
do
{
printf("\n\nEnter Choice ");
scanf("%d",&i);
// the rest of the switch is after this
} while (i != SOME_VALUE);
Note the use of the do loop, which tests the condition at the end, after a value has been read into i.
I would probably write a function that can be called in the loop:
while ((i = prompt_for("Enter choice")) != EOF)
{
switch (i)
{
case ...
}
}
And the prompt_for() function might be:
int prompt_for(const char *prompt)
{
int choice;
printf("%s: ", prompt);
if (scanf("%d", &choice) != 1)
return EOF;
// Other validation? Non-negative? Is zero allowed? Retries?
return choice;
}
You can also find relevant discussion at:
scanf() validation.
What is the reason for error while returning a structure in this C program?
Common macro to read input data and check its validity