For an assignment I am doing, I have to print out the initials from a string in C (or, an array of characters). To do this, I know that I need to find where the SPACE is, using (int)name[i] == 32 to find if the current character is a SPACE. My only issue with this is that I am having trouble figuring out how I can find the space, and then store the next character in the array of character. (e.g., user enters Mike Baggins, I have to print out MB). I will post my code below, to show you how far I've gotten. Please help, but please don't give me the full solution. Thank you!
#include <cs50.h>
#include <stdio.h>
#include <string.h>
int main(void)
{
string name = get_string(); // gets the user's input
char firstI = name[0]; // stores the first character from the user's input
int len = strlen(name);
if((int)firstI >= 97 && (int)firstI <= 122) // checks if the character is lowercase
{
firstI -= 32; // makes the value uppercase
}
for(int i = 0; i < len; i++)
{
if((int)name[i] == 32) // checks if the character is SPACE
{
printf("I found a space!\n"); // prints out "I found a space"
}
}
printf("%c\n", firstI); // prints out the first initial
}
It's actually simple, see this for example
#include <stdio.h>
#include <ctype.h>
int
main(void)
{
char array[10];
char string[] = "Mike Baggins";
int j;
// Always put the first non-whitespace
// character (we should probably skip all
// spaces first
array[0] = string[0];
// Now start at the character following the first
j = 1;
for (int i = 1; ((string[i - 1] != '\0') && (j < sizeof(array) - 1)); ++i) {
if (string[i - 1] == ' ') {
array[j++] = toupper(string[i]);
}
}
array[j] = '\0';
puts(array);
return 0;
}
All I needed was to know that strings are simply arrays with a special value marking the end of them → '\0'. Of course, you can improve it a lot. For instance, you could count how many initials are there in the input string and allocate enough space to store them all.
Also, this will only work if the interesting character follows the space immediately, but knowing that it's just an array I am sure you can figure out how to extend it to make it ignore consecutive spaces.
Related
I have been writing a program to input a phrase and turn it into an acronym. For some reason when I output my acronym at the moment it comes out with a bunch of random characters. How do I fix it?
#include <stdio.h>
#include <string.h>
#define MAXLEN 50
int main() {
int num;
printf("Enter number of acronyms to add to the database:");
scanf("%d", &num);
getchar();
char strings[num][MAXLEN];
char acronym[num][MAXLEN];
for(int i = 0; i < num; i++){
printf("Enter the string to convert into an acronym:");
fgets(strings[i],MAXLEN,stdin);
printf("%s\n", strings[i]);
for(int j = 0; j < 11; j++){
if((strings[i][j]) >= 'A' && (strings[i][j]) <= 'Z'){
char buffer[][20] = {strings[i][j]};
strcat(acronym[i], buffer[i]);
}
}
puts(acronym[i]);
}
return 0;
}
I have tried changing the MAXLEN value to see if it was a memory issue or like a buffer overload. I've also just tried changing around how the strings switch and work together but nothing has worked.
char buffer[][20] = {strings[i][j]};
Here you let the compiler count how many elements the array has from the initialization.
It has 1 element, A string with single a single character strings[i][j] and rest of the 20 byte array filled with 0.
strcat(acronym[i], buffer[i]);
Here you access buffer[i], but there is only one string there (as explained above), so this is invalid if i is anything but 0.
I'm not sure what you are trying to do, but this would be valid implementation of what this code tries to do:
// extract single character as a string
char buffer[2] = {strings[i][j], 0}; // only one of 2 and 0 is mandatory
// append it to acronym
strncat(acronym[i], 20, buffer);
Probably lots of other stuff there is wrong, but here is one definite issue and a possible solution.
I mixed up two programs in the cs50 sandbox, one was to find the the number of characters in an array and other was the print these characters. I know the program is garbage but could anyone explain me what is the compiler doing here?
When I ran this, the output starts printing alphanumeric text and never stops Thanks
#include <cs50.h>
#include <stdio.h>
#include <string.h>
int main(void)
{
string s = get_string("Name: ");
int n = 0;
while (strlen(s) != '\0')
{
n++;
printf("%c", n);
}
}
You have multiple problems with the code you show, here's a couple of them:
strlen(s) will never be zero as you never modify or remove characters from the string, which means you have an infinite loop
n is an integer and not a character so should be printed with the %d format specifier
'\0' is (semantically) a character, representing the string terminator, it's not (semantically) the value 0
To fix the first problem I suspect you want to iterate over every character in the string? Then that could be done with e.g.
for (int i = 0; i < strlen(s); ++i)
{
printf("Current character is '%c'\n", s[i]);
}
But if all you want is to could the number of characters in the string, then that's what strlen is already gives you:
printf("The number of characters in the string is %zu\n", strlen(s));
If you want to count the length of the string without using strlen then you need to modify the loop to loop until you hit the terminator:
for (n = 0; s[n] != '\0'; ++n)
{
// Empty
}
// Here the value of n is the number of characters in the string s
All of this should be easy to figure out by reading any decent beginners book.
while (strlen(s) != '\0') is wrong. '\0' equals 0. There string length is never 0, so the loop keeps going on forever, printing integers interpreted as characters.
You can either use the indexes to go through the string characters by using the variable "n" or you can increment the pointer of the string that you have received from the standard input to go through all of its characters.
#include <cs50.h>
#include <stdio.h>
#include <string.h>
int main(void)
{
string s = get_string("Name: ");
/* First way using n to iterate */
int n = 0;
for (n = 0; n < strlen(s); ++n)
{
printf("%c", s[n]);
}
printf("\n");
/* Second way increment the string pointer*/
while (strlen(s) != '\0')
{
printf("%c", *s); //print the value of s
s++; // go to the next character from s
}
printf("\n");
return 0;
}
this is what i tried.
this works properly for small string like wel$co*me
but gives weird output for pass#word. where am i going wrong exactly?
#include <stdio.h>
#include <string.h>
int main()
{
char s[100],rs[100];
int i,c=0;
scanf("%s",s);
int n = strlen(s);
for(i=0;i<n;i++)
{
if(((int)s[i] >= 65 && (int)s[i] <= 90) ||((int)s[i] >=97 && (int)s[i] <= 122) )
{
rs[c] = s[i];
c++;
}
else
{
continue;
}
}
printf("%s",rs);
return 0;
}
but gives weird output for pass#word. where am i going wrong exactly?
printf("%s",rs); expects rs to be a pointer to a string. Yet without a certain null character in the data pointed to by rs, the result is undefined behavior or in OP's case, "weird output".
A simple solution is
rs[c] = '\0'; // add this after the loop
printf("%s",rs);
Another important one is to avoid buffer overruns - use a width limit.
// scanf("%s",s);
scanf("%99s",s);
Code has other weaknesses, yet this are the key ones for now.
This seemed like a simple idea when I decided to try it out, but know it's driving me nuts.
I can reverse a whole string, but now I'm trying to reverse individual parts of a string.
Example:
"pizza is amazing" to "azzip si amazing"
Basically my program should reverse a string from point a to b, treating any words within it separately. My logic appears right (at least to me), but obviously something is wrong because my output is just the first word "pizza".
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char *reverse(char *a, int i, int j){ //reverse the words
char temp;
while(i<j){
temp = a[i];
a[i] = a[j];
a[j] = temp;
i++;
j--;
}
return a;
}
char *words(char *a, int i, int j){ // identify if there are any words from a-b
int count = i;
while(i<j){
if(a[i] == ' '){ // a space signifies the end of a word
reverse(a , i-count, i);
count = 0; //reset count for next word
}
i++;
count++;
}
return a;
}
int main(){
char a[50];
char *a2;
printf("Enter a string:\n); //string input
scanf("%s", a);
int strlength = strlen(a) + 1;
a2 = (char *)malloc(strlength*sizeof(char));
strcpy( a2, a);
printf("Reversed string:\n%s", words(a, 0, 4)); // create a-b range
return 0;
}
I realize my problem is most likely within words(). I am out of ideas.
Problem 1:
You should be more careful naming variables, understandable and meaningful names help the programmer and others reading your code. Keep in mind this is extremely important.
Problem 2:
When you pass the parameter %s to scanf(), it will read subsequent characters until a whitespace is found (whitespace characters are considered to be blank, newline and tab).
You can use scanf("%[^\n]", a) to read all characters until a newline is found.
For further reference on scanf(), take a look here.
Problem 3:
Take a look at the words() function, you're not storing a base index (from where to start reversing). The call to reverse() is telling it to reverse a single character (nothing changes).
You didn't specified if a whole word must be inside the range in order to be reversed or even if it is on the edge (ex: half in, half out). I'll assume the whole word must be inside the range, check out this modified version of the words() function:
char *words(char *str, int fromIndex, int toIndex){
int i = fromIndex;
int wordStartingIndex = fromIndex;
/*
It is necessary to expand the final index by one in order
get words bounded by the specified range. (ex: pizza (0, 4)).
*/
toIndex += 1;
/* Loop through the string. */
while(i <= toIndex){
if(str[i] == ' ' || str[i] == '\0' || str[i] == '\n'){
reverse(str, wordStartingIndex, i-1);
wordStartingIndex = (i + 1);
}
i++;
}
return str;
}
This should get you started. The function it is not perfect, you'll need to modify it in order to handle some special cases, such as the one I've mentioned.
The objective of my assignment is to take in user input string and then print out the English alphabetic characters (both lower case and upper case) that the user has entered.
For example if the user inputs:D_!an!_ i12el the output would be Daniel.
My approach was to loop through the input and just remove all the non alpha characters but I dont know how to.Please help with any ideas! This is what I have so far:
#include <stdio.h>
#include <string.h>
int main()
{
char my_array[100];
printf("Enter a message: ");;
while(strlen(gets (my_array)) == 0);
printf(" Your message is: %s\n", my_array);
for(int i = 0; i< strlen(my_array);i++)
{
if(my_array[i] < 'A' || my_array[i] > 'z')
{
my_array[i] = ' ';
}
}
printf(" Your new message is: %s\n", my_array);
}
EDIT:I got my loop working to print out only the alpha characters but it keeps adding extra characters when i print the elements. For example D_!a_*&Ni#32el becomes DaNielASCIIV. I dont know why this is happening.
for(int i = 0; i< 100;i++)
{
if (isalpha(message[i]))
{
putchar(message[i]);
}
}
Rather than trying to update the string you have, just print out a character if it's a letter.
Also, upper case and lower case characters don't immediately follow one another, so you need to check for them separately:
printf(" Your new message is: ");
for(int i = 0; i< strlen(my_array);i++)
{
if((my_array[i] >= 'A' && my_array[i] <= 'Z') ||
(my_array[i] >= 'z' && my_array[i] <= 'z'))
{
putchar(my_array[i]);
}
}
printf("\n");
Alternetely, you could replace the above if condition with a function that checks for this:
if (isalpha(my_array[i]))
EDIT:
The reason you're now seeing extra characters is because you changed the loop to loop over the entire array instead of the length of the string. Go back to using strlen(my_array) instead of 100 and you'll be fine.
Use this pattern for removing elements from an array
int i, j;
j = 0;
for (i=0;i<N;i++)
if (good(array[i]) )
array[j++] = array[i];
N = j;
We go through, adding everything that matches. It's efficient and in-place.
It might be better to loop through the input string and use strchr() to see if the characters are in the string "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz". This has the advantages of not relying on a specific ordering for of the letters of the alphabet (see here and here), and being flexible so that you can easily change the characters that you want to pick out. You could then collect the results in a string, or print the filtered characters out directly.
char my_array[100];
char filtered_array[100];
char alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
"abcdefghijklmnopqrstuvwxyz";
char *pchar;
int j = 0;
...
for (int i = 0; i < strlen(my_array); i++)
if ((pchar = strchr(alphabet, my_array[i])) != NULL) {
filtered_array[j] = *pchar;
++j;
}
filtered_array[j] = '\0';
...
The above code collects the results in a string. Note that a null-terminator is added to the end of filtered_array[], since this character would not be copied to the new array. If you want to include spaces or hyphens in the filtered string, just add these characters to the alphabet[] string.