I'm trying to get selected characters from one string into another. Everything looks okay, except the program keeps adding additional characters to the output. And it seems that it tends to add different number of these "unecessary" characters. Where might the problem be?
int main(void) {
int i,j=0;
char string[256];
char second_arr[256];
scanf("%255s", string);
for(i=0;i<256;i++){
if(string[i]=='('||string[i]=='['||string[i]=='{'){
second_arr[j]=string[i];
j++;
}
}
printf("%s", second_arr);
}
Say,
input: (hello)(}[} --->
Output:(([[H
Problem 1: You're not testing scanf for failure. It can return EOF, or zero to indicate the input didn't match your format string.
Problem 2: You're copying all 256 chars even if the user entered fewer, which means you're copying junk.
Problem 3: You're not adding a null terminator to second_arr.
Just do this:
if (scanf("%255s", string) != 1)
{
printf("scanf failed\n");
return 1;
}
for (i = 0; i < 256 && string[i]; i++) {
if(string[i]=='('||string[i]=='['||string[i]=='{'){
second_arr[j]=string[i];
j++;
}
}
second_arr[j] = '\0';
printf("%s", second_arr);
return 0;
Try this:
for (i=0; string[i]!=0; i++) // iterate the input string until the null-character
{
if (string[i] == '(' || string[i] == '[' || string[i] == '{')
second_arr[j++] = string[i];
}
second_arr[j] = 0; // set a null-character at the end of the output string
There is nothing to terminate the second string. Add
||string[i]=='\0'
to your conditions. Also break out of the loop when you see that null char, but only after you have copied it.
You should add at the end of second string second_arr the char '\n' to indicate its end.
Related
In C apparently strings are stored like an array with a null value or '\0' at the end. I wish to iterate over the string in a for loop and I need it to stop at '\0', not including it. I've tried many conditions for the if else and it all don't seem to work.
for example:
char patternInput[TEXTSIZE];
for(int i = 0; i<strlen(patternInput);i++)
{
if(patternInput[i]==NULL)
{
printf("\nlast character");
break;
}
else
{
printf("\n%c",patternInput[i]);
}
}
I've tried if(patternInput[i]==NULL), if(patternInput[i]==NUL),if(!patternInput[i]),if(patternInput[i]=='\0') and none of them seems to work.
If you're scanning the characters yourself, you can avoid the (redundant and somewhat expensive) strlen() call entirely, and instead use the value of patternInput[i] in the continuation-test of your for-loop:
char patternInput[TEXTSIZE] = "testing!";
for(int i = 0; patternInput[i] != '\0'; i++)
{
printf("\n%c",patternInput[i]);
}
printf("\nlast character\n");
Consider this code. This code prints 'Null character found' with position of the character. Notice the 'less than or equal to' in i<=strlen(str) in the loop invariant.
The last character at the length strlen + 1 is the '\0' character.
int i = 0;
char str[] = "Hello";
for(int i=0; i<=strlen(str); i++)
{
if(str[i]=='\0')
printf("Null character found at position %d", i);
}
I'm just starting to code and I need help figuring out why this loop counts spaces within a string.
To my understanding, this code should tell the computer to not count a space "/0" and increase count if the loop goes through the string and it's any other character.
int main(void)
{
string t = get_string("Copy & Past Text\n");
int lettercount = 0;
for (int i = 0; t[i] != '\0'; i++)
{
lettercount++;
}
printf("%i", lettercount);
printf("/n");
}
\0 represents the null character, not a space. It is found at the end of strings to indicate their end. To only check for spaces, add a conditional statement inside the loop.
int main(void)
{
string t = get_string("Copy & Past Text\n");
int lettercount = 0;
for (int i = 0; t[i] != '\0'; i++)
{
if (t[i] != ' ')
lettercount++;
}
printf("%i", lettercount);
printf("\n");
}
Space is considered a character, your code goes through the string (an array of characters) and counts the characters until it reaches the string-terminating character which is '\0'.
Edit: set an if condition in the loop if(t[i] != ' ') and you wouldn't count the spaces anymore.
You misunderstand the nature of C strings.
A string is an array of characters with a low value ( '\0') marking the end of the string. Within the string some of the characters could be spaces (' ' or x20).
So the " t[i] != '\0' " condition marks the end of the loop.
A simple change:
if ( t[i] != ' ') {
lettercount++;
}
Will get your program working.
This for loop
for (int i = 0; t[i] != '\0'; i++)
iterates until the current character is the terminating zero character '\0' that is a null character. So the character is not counted.
In C there is the standard function isalpha declared in the header <ctype.h> that determines whether a character represents a letter.
Pay attention to that the user can for example enter punctuation symbols in a string. Or he can use the tab character '\t' instead of the space character ' '. For example his input can look like "~!##$%^&" where there is no any letter.
So it would be more correctly to write the loop the following way
size_t lettercount = 0;
for ( string s = t; *s; ++s )
{
if ( isalpha( ( unsigned char )*s ) ) ++lettercount;
}
printf("%zu\n", lettercount );
This statement
printf("/n");
shall be removed. I think instead you mean
printf("\n");
that is you want to output the new line character '\n'. But this character can be inserted in the previous call of printf as I showed above
printf("%zu\n", lettercount );
A null-terminator is the last leading element in a character array consisting of a string literal (e.g. Hello there!\0). It terminates a loop and prevent further continuation to read the next element.
And remember, a null-terminator isn't a space character. Both could be represented in the following way:
\0 - null terminator | ' ' - a space
If you want to count the letters except the space, try this:
#include <stdio.h>
#define MAX_LENGTH 100
int main(void) {
char string[MAX_LENGTH];
int letters = 0;
printf("Enter a string: ");
fgets(string, MAX_LENGTH, stdin);
// string[i] in the For loop is equivalent to string[i] != '\0'
// or, go until a null-terminator occurs
for (int i = 0; string[i]; i++)
// if the current iterated char is not a space, then count it
if (string[i] != ' ')
letters++;
// the fgets() reads a newline too (enter key)
letters -= 1;
printf("Total letters without space: %d\n", letters);
return 0;
}
You'll get something like:
Enter a string: Hello world, how are you today?
Total letters without space: 26
If a string literal has no any null-terminator, then it can't be stopped from getting read unless the maximum number of elements are manually given to be read till by the programmer.
I am currently trying to figure out how to process an input of such format: [int_1,...,int_N] where N is any number from interval <1, MAX_N> (for example #define MAX_N 1000). What I have right now is fgets to get it as string which I then, using some loops and sscanf, save into an int array.
My solution is, IMO, not the most elegant and functional, but that's because of how I implement it. So what I'm asking I guess is how you guys would solve this problem, because I've ran out of ideas.
Edit: adding the code for string -> int array
int digit_arr[MAX_N];
char input[MAX_N];
//MAX_N is a constant set at 1000
//Brackets and spaces have been removed at this point
for (i = 0; i < strlen(input); i++) {
if(sscanf(&input[i+index_count],"%d,", &digit_arr[i]) == 1){
while (current_char != ',') {
current_char = input[i+index_count+j];
index_count++;
j++;
if ((index_count+j+i) == strlen(input)-1){
break;
}
}
}
My personal variant:
char const* data = input; // if input is NOT a pointer or you yet need it unchanged
for(;;)
{
int offset = 0;
if(sscanf(data, "%d,%n", digit_arr + i, &offset) == 1)
{
++i;
if(offset != 0)
{
data += offset;
continue;
}
}
break;
}
You might finally ckeck if all characters in the text are consumed:
if(*data)
{
// not all characters consumed, input most likely invalid
}
else
{
// we reached terminating null character -> fine
}
Note that my code as is does not cover trailing whitespace, you could do so by changing the format string to "%d, %n (note the added space character).
My program aims to print each word in the sentence on a separate line.but I should print it with %s not %c! I already try to implement it but the program does not give me a correct output ! my idea is when you find null character
1- print the word
2- return the index of the temp array to 0 and store a new word
int main () {
char sen[100];
char cpy [100];
printf("Entter a sentence ");
gets(sen);
int len = strlen(sen);
int i = 0;
int k =0;
for (i=0 ; i<len;i++)
{
if (sen[i]!='\0')
{
cpy[k++]+=sen[i];
}
else{
printf("%s\n",cpy);
k=0;}
}
}
You confound null character and space character. Null character \0 stands for "end of string" : the strlen function returns the number of characters before the first \0.
In your forloop, you want to display each word separated by so you have to test with the caracter instead of \0.
Also to correctly display your string you have to end the string with the \0 character. So before the instruction printf you must do cpy[k] = '\0';.
if (sen[i]!='\0') will always be true as pointed by Julien Vernay, you need if (sen[i]!= ' ') instead of if (sen[i]!='\0'), as there are spaces between words, to seprate them.
Also in cpy[k++]+=sen[i]; you are adding sen[i] to cpy[k++] which seams weird, I think what you need is cpy[k++] = sen[i];
Modify your loop as follows...
for (i=0 ; i<len; i++) {
int flag = 0;
while(sen[i] == ' ') i++; // multiple spaces
while(sen[i] != ' ' && sen[i] != '\0') {
cpy[k++] = sen[i];
flag = 1;
i++;
}
if(flag) {
cpy[k] = '\0';
printf("%s\n",cpy);
k=0;
}
}
You can have to not bother with doing a copy - all you need to do is essentially replace spaces with new lines. So here is the code to do this:
#include <stdio.h>
int main()
{
char sen[100];
bool last_char_space = true;
printf("Please enter a sentence: ");
fflush(stdout);
fgets(sen, 100, stdin);;
for (int loop = 0; sen[loop]; ++loop) { // send[loop] is true until end of string - saves repeatedly calling strlen
if (send[loop] == ' ') { // A space
if (last_char_space) { // Last character not a space, put new line
fputc('\n', stdout);
}
last_char_space = true; // Record the fact that we are between words
} else {
fputc(sen[loop], stdout); // Not a space - print it
last_char_space = false; // We are working on a word
}
}
return 0;
}
why following code is giving garbage value ?
here I am trying to get an string as an input from user character by character. In the following code i have got input from user and stored in string[] array then in order to do some other operations i have stored the same in other array called temp_string[i]. But surprisingly i am getting garbage value in output.and also length calculated using strlen is not correct. can anybody look at this code and explain whats going wrong?
#include<stdio.h>
#include<stdio.h>
int main()
{
char ch;
int i = 0, j = 0;
int length = 0;
int lengthsb = 0;
char string[100];
printf(" Enter the string to divide\n ");
while(ch != '\n')
{
ch = getchar();
string[i] = ch;
i++;
}
char temp_string[i];
printf("%s", string);
i = 0;
while(string[i] != '\n')
{
temp_string[i] = string[i];
i++;
}
length = strlen(temp_string);
printf("Entered string is %s and its length is %d\n", temp_string, length);
}
You forgot to add the null at the end of the string.
C strings are null-terminated, that means that all operations in c strings expect a null to mark the end of the string, including functions like strlen.
you can achieve that just adding:
string[i] = '\0';
After fill the string.
Another thing, what happens if the user enters a string bigger than 100? Is good to validate the input for these cases, otherwise you can get a buffer overflow.
You need to add a NULL - terminated at the end of your string. Add \0.
You need to put a '\0' char at the end of the string so strlen(), printf() and other C functions dealing with strings will work. That is how the C API knows it reached the end of the string.
Also, you don't want to set new characters at the memory space past the string array. So you better check that in your loop (and save a last array item to set the '\0').
while (ch != '\n' && i < 99)
{
ch = getchar();
string[i] = ch;
i++;
}
string[i] = '\0'; // set the string terminator past the end of the input
Remember to do the same after copying the characters to temp_string. (By the way, you can replace that loop with a call to strcpy(), that does exactly that, except it will end only when it finds a '\0'.)
You might also want to read What's the rationale for null terminated strings?
Here is your Final Code:
#include<stdio.h>
#include<stdio.h>
#include<string.h>
int main()
{
char ch;
int i = 0, j = 0;
int length = 0;
int lengthsb = 0;
char string[100];
char temp_string[100];
printf(" Enter the string to divide\n ");
while(ch != '\n')
{
ch = getchar();
string[i] = ch;
i++;
}
string[i]=NULL;
printf("%s", string);
i = 0;
while(string[i] != '\0')
{
temp_string[i] = string[i];
i++;
}
temp_string[i]=NULL;
length = strlen(temp_string);
printf("Entered string is %s and its length is %d\n", temp_string, length);
}
In the above code what exactly you are missing is NULL or '\0' termination of the string. I just added it to make it useful.