The program runs and exits with code 0, but gives no output, it's supposed to be a linear search program
I looked to other similar problems, i tried to end the array with \n. tried instead of just relying in just the "if (strcmp=0)" to make something with the values strcmp return, I'm very new and for what I'm learning not very good, just made things worst, i tried to look if it was about the char* values strcmp expect, but couldn't find the problem
#include <stdio.h>
#include <string.h>
#define max 15
int lineal(char elementos[], char elebus)
{
int i = 0;
for(i=0; i<max; i++)
{
if(strcmp(elementos[i], elebus)==0)
{
printf("Elemento encontrado en %d,", i); //element found in
}
else
{
printf("elemento no encontrado"); //not found
}
}
}
int main()
{
char elebus[50];
char elementos[max][50]= {"Panque", "Pastel", "Gelatina", "Leche", "Totis", "Tamarindo" "Papas", "Duraznos", "Cacahuates", "Flan", "Pan", "Yogurt", "Café", "Donas", "Waffles"};
printf("Escribir elemento a buscar\n");
scanf("%s", elebus);
int lineal(char elementos[], char elebus);
}
The expected output would be element found in "i" position, if found
if not found print "not found"
You want to pass it a string to find, not just one character Also, elementos should be a 2D array. Change the signature of your function to this:
int lineal(char elementos[max][50], char *elebus)
Also, in main, you don't call the function. Instead, you just declare it again. call it like this:
lineal(elementos, elebus);
Furthermore, I would change it to return void instead of int. You're neither returning anything (that's undefined behavior) nor are you using the return value anywhere. But I assume that this isn't the final version and you want to return the index at some point.
On a side note, right now it's printing that it didn't find the element for every time it didn't match, even if it does find it eventually. I would recommend this instead:
for (i = 0; i < max; i++)
{
if (strcmp(elementos[i], elebus) == 0)
{
printf("Elemento encontrado en %d\n,", i); //element found in
return;
}
}
printf("elemento no encontrado\n"); //not found
This is printing "elemento no encontrado" only once, and only when the string wasn't found.
Related
Searching for program for defanging an IP address(only with strings)
EX:
Input : 12.34.57.34
Output : 12[.]34[.]57[.]34
#include<stdio.h>
#include<string.h>
int main()
{
char a[20],IP[3];
fgets(a,sizeof(a),stdin);
int s=strlen(a),i;
for(i=0;i<s;i++)
{
if(a[i]=='.')
{
a[i]=a[i+1];
printf("[.]);
}
printf("%c",a[i]);
}
return 0;
}
I've got close
if(a[i]=='.')
{
a[i]=a[i+1];
printf("[.]);
}
You replaced the dot with the number immediately after it, which I don't think is intended behavior:
123.123 becomes 1231123, so you'll be printing out 123[.]1123
Make it so that when you detect a dot, you just print out "[.]", and then go on to the next character (so basically just print "[.]" and do nothing). No need to replace the character, or print it out afterwards.
I'm pretty new to coding and especially to C, so I decided to take the CS50 course as an introduction to the language. I just finished watching the first lecture on C and, as a means to test my knowledge on the subject, I attempted to write a short little program. Also I am using the course's library for the get_int() function.
The goal is to test the user's input and check if it's less or equal to ten. If it matches the parameters, the program should print the "Success!" message and exit; otherwise, it should ask for input again. If the input value is over 10, the program responds just as expected, but if you input a value of 10 or less, it ends up asking you for input one more time before actually exiting. I think it's probably something with the "for" loop, but I just can't figure it out.
My code:
#include <stdio.h>
#include <cs50.h>
#include <stdlib.h>
int check_for_value();
int main()
{
for(check_for_value(); check_for_value() != 1; check_for_value())
{
printf("Failed!\n");
}
exit(0);
}
int check_for_value()
{
int i = get_int("Your value: \n");
if(i <= 10)
{
printf("Success!\n");
return 1;
}
else
{
printf("Try again!\n");
return 0;
}
}
That isn't doing exactly what you think it is. In your for loop, each time you write check_for_value(), it is going to call that function. So it will call it the first time and the return value will not matter. It will call it again for the middle statement and then the value will matter because you are comparing the output to not equal to 1. And then again it will call the function in the third statement, where again it won't matter. Usually for something like this, you would use a while loop instead. An example below:
int ret = check_for_value();
while(ret != 1) {
printf("Failed\n");
ret = check_for_value();
}
printf("Success\n");
Technically a for loop can work too as the following:
for(int ret = check_for_value(); ret != 1; ret = check_for_value()) {
printf("Failed\n");
}
The for loop can look very simply
for ( ; !check_for_value(); )
{
printf("Failed!\n");
}
In such a case it is better to use the while loop
while ( !check_for_value() )
{
printf("Failed!\n");
}
As for your for loop
for(check_for_value(); check_for_value() != 1; check_for_value())
^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^
then the underlined calls of the function are not tested.
Also bear in mind that such a definition of a for loop
for(int ret = check_for_value(); ret != 1; ret = check_for_value()) {
printf("Failed\n");
}
is a very bad style of programming. There is redundant records of the function calls. The intermediate variable ret is not used in the body of the loop. So its declaration is also redundant. Never use such a style of programming.
Pay attention to that according to the C Standard the function main without parameters shall be declared like
int main( void )
and the statement
exit( 0 );
is redundant.
Edit 2: I realized that I did not have a "Not found" result for any query not in the database. Changes have been made to introduce this feature. Here is the current test and test output:
Input:
3
sam
99912222
tom
11122222
harry
12299933
sam
edward
harry
Output:
Not found
=0
Not found
=0
Not found
=0
Not found
=0
sam
=99912222
Not found
=0
Not found
=0
Not found
[Infinite loop continues]
Edit: I have changed a few things in the while loop in display(). I am now getting an infinite loop printing "=0" except for the third or fourth cycle through the search. Hmmm...
By the way, thanks for the reminder of testing strings with ==. Seems like a no-brainer now.
I have done some searching and have yet to be able to understand where I have gone wrong with my code. I am working on a challenge which will result in a simple phone-book program. It will take input of a number (the number of entries to be added) then the names and associated phone numbers (no dashes or periods). After the entries have been added then the user can search for entries by name and have the number displayed in the format "name=number".
The code throws a segmentation fault with the while loop in the display() function. I assume that I am attempting to print something assigned as NULL, but I cannot figure out where I have gone wrong. Any help would be very appreciated.
Lastly, the challenge calls for me to read queries until EOF; however, this confuses me since I am to accept user input from stdin. What does EOF look like with stdin, just a register return (\n)?
(PS: This is my first attempt at linked lists, so any pointers would be greatly appreciated.)
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>
void add_entry(void);
void display(void);
struct phonebook {
char name[50];
int number;
struct phonebook *next;
};
struct phonebook *firstp, *currentp, *newp;
char tempname[50];
int main() {
int N;
firstp = NULL;
scanf("%d", &N);
for (int i = 0; i < N; i++) {
add_entry();
}
display();
return 0;
}
void add_entry(void) {
newp = (struct phonebook*)malloc(sizeof(struct phonebook));
if (firstp == NULL) firstp = currentp = newp;
else {
currentp = firstp;
while (currentp->next != NULL)
currentp = currentp->next;
currentp->next = newp;
currentp = newp;
}
fgets(currentp->name, 50, stdin);
scanf("%d", ¤tp->number);
currentp->next = NULL;
}
void display(void) {
while (strcmp(tempname, "\n") != 0) {
currentp = firstp;
fgets(tempname, 50, stdin);
while (strcmp(currentp->name, tempname) != 0) {
if (currentp->next == NULL) {
printf("Not found\n");
break;
}
currentp = currentp->next;
}
printf("%s=%d\n", currentp->name, currentp->number);
}
}
Your problem is that you never find the entry you're looking for. The expression currentp->name != tempname will always be true, since those are always unequal. In C, this equality test will not compile into a character-by-character comparison, but into a comparison of pointers to currentp->name and tempname. Since those are never at the same addresses, they will never be equal.
Try !strcmp(currentp->name, tempname) instead.
The reason you crash, then, is because you reach the end of the list, so that currentp will be NULL after your loop, and then you try to print NULL->name and NULL->number, actually causing the crash.
Also, on another note, you may want to start using local variables instead of using global variables for everything.
Not sure if this solves the problem, but you can't directly compare strings with != in C. You need to use if( strcmp( string1, string2 ) == 0 ) to check.
fgets doesn't take EOF (= -1) like getchar does, but it does include '\n' and pad the rest with NULL (= 0) so checking for EOF is not really helpful, but yes you can stop after \n or NULL.
I have scanned "ABCDEFGHIJK" with fscanf into a char array[26]. Then I got "ABCDEFGHIJK" using "for" into another array[11]. Now I need to get to an "ABCDEFGHIJK.mp4" array[15] in order to feed that filename into a rename function.
I don't know much about C programming besides printf, scanf, for and while.
sprintf(filename, "%c%c%c%c%c%c%c%c%c%c%c.mp4", codigo[0], codigo[1], codigo[2], codigo[3], codigo[4], codigo[5], codigo[6], codigo[7], codigo[8], codigo[9], codigo[10]);
This code above seems to work, but I wonder if there is a simpler way (especially for bigger arrays)?
Clarification: I have a txt file, formatted with these containing the filenames without extension and the human filename. I'm trying to make a program that will rename these files to the correct name, as they are from a backup that failed.
EDIT: Here is the full program. I renamed the variables to make more sense, so "codigo" is now "idcode".
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(void)
{
int i, j, k;
char value1[26], value2[70], idcode[11], filename[16], fullname[64], filenamestring[16], fullnamestring[64];
// Opening file.
FILE *nomes;
nomes = fopen("/Users/EA/Desktop/Songs/backup.txt", "rt");
if(nomes == NULL)
{
printf("Erro ao abrir backup.txt");
exit(1);
}
// Skipping beggining of file until first value.
for(i=0; i<10; i++)
{
fscanf(nomes, "%*s");
}
// Reading first value, and repetition.
while(fscanf(nomes, "%s", value1) == 1)
{
j = k = 0;
// Extracting idcode from value1.
for(i=7; i<18; i++)
{
idcode[j] = value1[i];
j++;
}
// Filling the complete filename.
sprintf(filename, "%.*s.mp4", 11, idcode);
// Reading second value, the "human" filename.
fscanf(nomes, "\n%[^\n]", value2);
for(i=6; i<70; i++)
{
fullname[k] = value2[i];
k++;
}
// Transforming filenames into strings for rename function.
strncpy(filenamestring, filename, 16);
strncpy(fullnamestring, fullname, 64);
// Renaming the files.
rename(filename, fullname);
// Skipping useless data before the next cycle.
for(i=0; i<9; i++)
{
fscanf(nomes, "%*s");
}
}
// Closing file and ending program.
fclose(nomes);
return(0);
}
It looks like you got an array of char's.
You can simply do:
sprintf(filename, "%.*s.mp4", 11, codigo)
You can read more about the %.*s specifier in this question.
If you just want to append the format ".mp4" to the end of the string the easiest way to do that is just:
strcat(filename,".mp4");
after you printed the name without the ".mp4" into it.
If you really want to use sprintf then i think this should suffice:
sprintf(filename,"%s.mp4", codigo);
Also,if you want your string to be bigger and not fixed in size you can put "\0" at the end of it(this might not work if you try to use the strings in other programming languages but c) with strcat as above,or you can do this:
memset(&filename, 0, sizeof(filename));
I have an assignment where I am supposed to use this very very simple (or so I thought) stack that my teacher wrote in C, just using an array. From this, I have to implement reverse polish notation from a text file.
In order for me to implement this, I am using a stack, pushing values on until I hit an operation. I then do the operation and push the result back onto the stack until the user hits p to print the value.
The problem is, for some reason, my professor's implementation of the stack array defaults the first (index 0) value to 0. Printing the stack without pushing anything onto it should result in null but it appears the output is 0.
Here is my professor's implementation of the stack:
#define STK_MAX 1024
#define ELE int
ELE _stk[STK_MAX];
int _top = 0;
void stk_error(char *msg)
{
fprintf(stderr, "Error: %s\n", msg);
exit(-1);
}
int stk_is_full()
{
return _top >= STK_MAX;
}
int stk_is_empty()
{
return _top == 0;
}
void stk_push(ELE v)
{
if ( stk_is_full() )
stk_error("Push on full stack");
_stk[_top++] = v;
}
ELE stk_pop()
{
if ( stk_is_empty() )
stk_error("pop on empty stack");
return _stk[--_top];
}
void print()
{
for(int i = 0; i <= _top; ++i)
printf("%d ", _stk[i]);
printf("\n");
}
I realize that the print statement will print a value that has not been pushed yet, but the problem is, is that when I don't print it, it still ends up there and it ends up screwing up my rpn calculator. Here is what happens when I do this:
// input
stk_push(2);
print();
stk_push(4);
print();
// output
2 0
2 4 0
How do I get rid of the 0 value that is affecting my calculator? Doing stk_pop() after the pushing the first value onto the stack didn't seem to work, and checking that top == 0, then directly inserting that element before incrementing _top didn't work.
When you are printing, loop from 0 to (_top - 1), since your top most element is actually at _top - 1. Hint : Look at your pop/push method.
void print()
{
for(int i = 0; i < _top; ++i)
printf("%d ", _stk[i]);
printf("\n");
}
"The problem is, is that the rpn calculator relies on the TOS being accurate. When I do pop() though, it will pop 0 and not the real TOS."
Sounds like a problem with your calculator implementation. You assumed the top of the stack would be null, but that's not the case for your professors stack implementation. Simply a invalid assumption.
Instead he's provided a stk_is_empty() method to help determine when you've pop everything.
If you need to pop all elements, you'll need to break on the condition of stk_is_empty().
stk_push(2);
stk_push(4);
while( stk_is_empty() == false)
{
stk_pop();
}
Of course in reality you'd be setting the pop return to a variable and doing something with it. The key point is leveraging stk_is_empty().
I haven't written C++ in few years so hopefully I didn't make a minor syntax error.