I wrote a function that removes a given char from a string.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char* input_long(void);
void removeChar(char str[], char ch);
void main()
{
char *str, ch;
str=input_long();
printf("\nplease enter a char to be removed from the string: ");
scanf("%c", &ch);
removeChar(str, ch);
printf("the string after the removal is %s \n", str);
free(str);
}
void removeChar(char str[], char ch) //this function removing a given char from a given string//
{
int i,j = 0;
for (i = 0; str[i] != '\0'; i++) //looping the string until its end//
{
if (str[i] != ch) //by that we ensure the char will be erased from the string //
{
str[j] = str[i];
j++;
}
}
str[j]='\0'; //the end of the new string after the whole process//
}
char* input_long(void) //this function gets a string dynamically allocated//
{
char tempstr[80], *str;
printf("enter a string\n");
gets(tempstr);
str=(char*)malloc((strlen(tempstr)+1)*sizeof(char));
strcpy(str,tempstr);
return str;
}
My code didn't run well; when I ran it, it seemed to lead the statement which asks the user to enter a string. I repaired the code by adding _flushall() , and now the code is running well:
_flushall
str=input_long();
printf("\nplease enter a char to be removed from the string: ");
scanf("%c", &ch);
I don't really understand why adding that statement indeed repaired it.
Related
I have tried make a program which is fills up a string array with string that is given by the user and after that i run into a problem with the idea that how coud i examine that how many words are in the array. I examined the whitespace characterts but it does not work well, i guess .Because whatever the array contains ,it writes flase value : e.g its contain 2 words when there is only 1 word in it.
int db =0;
char array[255];
void string(char str[]){
printf("Enter a string:");
scanf("%s",str);
}
void words(char str[]){
int i=0;
int len = strlen(str);
while( str[i]!=len)
{
if(str[i]==' ')
db++;
i++;
}
}
int main(int argc,char** argv){
string(array);
words(array);
printf("its contain %d words",db);
}
You have a few problems, but the main is using scanf instead of gets. If you'll run this function you'll see that scanf fails to read beyond whitespace, where gets doesn't: (my input was "123 456 789")
void string(char str[]){
printf("Enter a string:");
scanf("%s",str);
printf("%s\n", str); // the string was scanned until 1st whitespace
gets(str);
printf("%s\n", str); // proper string was read
}
The 2nd thing to note is warnings. The return type of strlen() isn't int, it's size_t (man). Also, you are comparing not matching types (char != int):
void words(char str[]){
int i=0; // change to size_t because it is checked against len
int len = strlen(str); // change to size_t
while( str[i]!=len) // should be i != len because you check the location in the string against the length, not against the char itself!!
{
if(str[i]==' ')
db++;
i++;
}
}
The 3rd thing is logic. What if your string has indeed 2 words: "hello world"? you would only count white_spaces and assume you have only one word. I would add something like:
void words(char str[]){
size_t i=0;
size_t len = strlen(str);
printf("%s\n", str);
while(i!=len)
{
if(str[i]==' ')
db++;
i++;
}
if(i) // if i is positive, there must have been a white_space -> add the 1st word because it wasn't counted (Assuming the string must start with a word and not a white_space!!)
i++;
}
This is how I would rewrite it:
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
int db =0;
char array[255];
void string(char str[]){
printf("Enter a string:");
gets(str);
}
void words(char str[]){
size_t i = 0;
size_t len = strlen(str);
while(i != len)
{
if(str[i]==' ')
db++;
i++;
}
if(i)
i++;
}
int main(/*no need for argc, argv. You can leave them there, but I prefer to omit if not used*/){
string(array);
words(array);
printf("its contain %d words",db);
return 0;
}
Note that there are still some issues:
What happens if more than one white space is entered between 2 words?
What happens if a white space is the first char (I assumed not, but can it be?)
What happens if the input string is too long?
Analyse main() function
int main(int argc,char** argv){
string(array);
words(array);
printf("its contain %d words",db);
}
when you are calling words(array) function what is array ? nothing. if you are taking array as a global then what's the the needs of passing to function & catching with str .
Next,
void string(char str[]){
printf("Enter a string:");
scanf("%s",str);
}
modify above function as below if you want to scan strings with white spaces.
void string(char str[]){
int len;//define it
fgets(str,len,stdin);//TO READ STRINGS WITH WHITESPACES
}
Next come to your logic, what you want to achieve with while( str[i]!=len) ?
Rotate loop upto NULL & and then modify the condition for finding no of words as below.
void words(char str[]){
int i=0;
// int len = strlen(str);
while( str[i]! = NULL)
{
if(str[i]==' ' && str[i+1] !=' ')
db++;
i++;
}
}
complete program as
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
void words(char str[]);
int db =0;
char array[255];
void string(char str[]){
int n;// define it
printf("Enter a string:");
fgets(str,n,stdin);// now data is there in str not in array variable thats why call words() function from here only it's a better option
words(str);// call from here bcz now you have str
}
void words(char str[]){
int i=0;
printf("string = %s \n",str);
while( str[i] != '\0')
{
if( (str[i]==' ' && str[i+1] !=' ') || str[i+1] == '\0')
db++;
i++;
}
printf("db = %d \n",db);
}
int main(int argc,char** argv){
string(array);
printf("its contain %d words",db);
}
I hope it will helps.
I thought it's the easiest one. You have to start with your counter
int db = 1;
I wrote a function that remove a given char from a string.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char* input_long(void);
void removeChar(char str[], char ch);
void main()
{
char *str, ch;
str = input_long();
printf("\nplease enter a char to be removed from the string: ");
scanf("%c", &ch);
removeChar(str, ch);
printf("the string after the removal is %s \n", str);
free(str);
}
void removeChar(char str[], char ch) //this function removing a given char from a given string//
{
int i, j = 0;
for (i = 0; str[i] != '\0'; i++) //looping the string until its end//
{
if (str[i] != ch) //by that we ensure the char will be erased from the string //
{
str[j] = str[i];
j++;
}
}
str[j] = '\0'; //the end of the new string after the whole process//
}
char* input_long(void) //this function gets a string dynamically allocated//
{
char tempstr[80], *str;
printf("enter a string\n");
gets(tempstr);
str = (char*) malloc((strlen(tempstr) + 1) * sizeof(char));
strcpy(str, tempstr);
return str;
}
My code didnt run well; when I run it, it seemed to lead the statement which asks the user to enter a string. I repaired the code by adding _flushall() , and now the code is running well:
_flushall();
str=input_long();
printf("\nplease enter a char to be removed from the string: ");
scanf("%c", &ch);
I dont really understand why adding that statement indeed repaired it.
I want to capitalize the first character of a pointer string.
For example, input: john
Output: John
I can do it with arrays (s[0] = toUpper(s[0]), but is there a way to do it with pointers?
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#define MAX 30
int transform(char *s)
{
while (*s != '\0')
{
*s = toupper(*s);
s++;
}
return *s;
}
int main()
{
printf("String: ");
char *s[MAX];
getline(&s,MAX);
transform(s);
printf("Transformed char: %s", &s);
}
int getline(char *s, int lim)
{
int c;
char *t=s;
while (--lim>0 && (c=getchar())!=EOF && c!='\n') *s++=c;
*s='\0';
while (c!=EOF && c!='\n')
c=getchar();
return s-t;
}
This code turns the whole string to upper case.
Your transform function is looping through the entire string and running toupper on each one. Just run it on the first character:
void transform(char *s)
{
*s = toupper(*s);
}
Also, you declare s in main as an array of pointers to char. You just want an array of char:
int main()
{
printf("String: ");
char s[MAX];
getline(s,MAX); // don't take the address of s here
transform(s);
printf("Transformed char: %s", s); // or here
}
You want to move main to the end of the file as well, so that getline is defined before it is called.
Easy solution:
void transform(char* p) {
//Only first character
*p = toupper(*p);
}
//Call like that:
char str[] = "test";
transform(str); //str becomes: "Test"
I tried to compile and run the following program to reverse a string using the gcc compiler for linux but it shows the error : segmentation fault (core dumped).I even tried to debug using gdb but it didn't help. The program given below firstly inputs t which is the number of test cases.I tested the program with 3 test cases but after taking the 2nd input from user, the compiler shows error.
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
char* strrev(char*);
int main(int argc, char *argv[])
{
int t,i=0,temp=0;
char *str[10],*rev[10];
scanf("%d",&t); //input the number of test cases
while(i<t)
{
scanf("%s",str[i]);
i++;
}
while(temp<t) //reverse the string and display it
{
rev[temp]=strrev(str[temp]);
printf("%s \n",rev[temp]);
temp++;
}
return 0;
getchar();
}
Function to reverse the string:
char *strrev(char *str)
{
int i = strlen(str)-1,j=0;
char ch;
while(i>j)
{
ch = str[i];
str[i]= str[j];
str[j] = ch;
i--;
j++;
}
return str;
}
You are getting segmentation fault because you haven't allocated space for elements of str.
You need to allocate memory first in main function.
scanf("%d",&t); //input the number of test cases
if(t <= 10)
for(size_t i = 0; i < t; i++)
str[i] = malloc(50); // Assuming string is no more than 50characters.
else
exit(0);
Beside this there are many flaws in your code. Here is the code after fixing them
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
void strrev(char*); // Change return type to void
int main(void)
{
int t,i=0,temp=0, ch;
char *str[10];
scanf("%d",&t); //input the number of test cases
while((ch = getchar()) != EOF && ch != '\n'); // To consume newline character after scanf
// Allocate memory for str elements
if(t <= 10)
for(size_t i = 0; i < t; i++)
str[i] = malloc(50); // Assuming string is no more than 50characters.
else
exit(0);
i = 0;
while(i < t)
{
fgets(str[i],50,stdin); // Use fgets instead of scanf to read string
i++;
}
while(temp<t) //reverse the string and display it
{
// Since you are reversing string by flipping the characters the same
// string just pass pointer to it. str[temp] will be updated in function.
strrev(str[temp]);
printf("Reverse is %s \n", str[temp]);
temp++;
}
return 0;
}
void strrev(char *str)
{
size_t i = strlen(str)-1,j=0;
char ch;
while(i>j)
{
ch = str[i];
str[i]= str[j];
str[j] = ch;
i--;
j++;
}
//printf("Reverse is %s \n", str);
}
you have missed to allocate memory before reading char* value, so you can do this:
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
char* strrev(char*);
int main(int argc, char *argv[])
{
int t,i=0,temp=0;
char *str[10],*rev[10];
scanf("%d",&t); //input the number of test cases
while(i<t)
{
str[i] = (char*)malloc(100); // just allocate memory
scanf("%s", str[i]);
i++;
}
while(temp<t) //reverse the string and display it
{
rev[temp]=strrev(str[temp]);
printf("%s \n",rev[temp]);
temp++;
}
return 0;
getchar();
}
char *str[10],*rev[10];
You did not assign storage to hold string values yet for those pointers.
char * str; /* this is a string pointer */
char * str = malloc(15); /* this creates storage for a string */
char str[10]; /* this creates a static char array, also is a string */
I also had the same issue. I just fixed it by correcting the indices of the matrix.
#include <stdio.h>
main()
{
char* str;
char* strrev;
int i = 0;
int j = 0;
int c;
printf("Enter the string\n");
scanf("%[^\n]%*c", str);
while (*(str + i) != '\n')
{
i++;
}
for (c = i; c >= 0; c--)
{
*(strrev + j) = *(str + c);
j++;
}
}
This is my code to reverse a string. When I compile the code , it gives an error segmentation fault . Someone plz help me understand the error and realize my mistake.
Thanks
There are many issues:
You never allocate memory for str or strrev. This is why it crashes; writing to uninitialized pointers invokes undefined behavior, often resulting in a seg fault.
You're using scanf() with a complex conversion when you could just use fgets().
You should use strlen() rather than looping to find the end of the string.
char *str,*strrev;
first your char buffers where never initialized.
http://www.cplusplus.com/reference/cstring/strlen/
second use strlen to determine string len
regards
In addition to #unwind, even if you used str[100], the loop to find the length will fail. Since str doens not have a \n, the while() loop never ends.
// bad
char str[100];
scanf("%[^\n]%*c", str);
while (*(str + i) != '\n') {
i++;
}
// better
char str[100];
scanf("%99[^\n]%*c", str);
while (*(str + i) != '\0') { // look for \0
i++;
}
Following (some of) #unwinds pointers, here is some code that will reverse a string:
(you can use scanf(), but do not need such a complicated format string)
#include<stdio.h>
main()
{
char str[260],strrev[260];
int i=0, len;
printf("Enter the string\n");
scanf("%s",str);
len = strlen(str);
for(i=1;i<len;i++)
{
strrev[i-1] = str[len-i];
}
strrev[len]=0;
;
}
If you would like to avoid using scanf, then replace it with something like:
char str[260], strrev[260];
//...
fgets(buf, sizeof(str), stdin);
[EDIT-per comment] If still want to use a char *, do something like this:
#include<stdio.h>
main()
{
char *str, *strrev;
int i=0, len;
printf("Enter the string\n");
str = malloc(260);
strrev = malloc(260);
scanf("%s",str);
len = strlen(str);
for(i=1;i<len;i++)
{
strrev[i-1] = str[len-i];
}
strrev[len]=0;
free(str);
free(strrev);
}
Note: Other than keystroke counting, I am not sure how you would determine at run-time just how many characters will be entered by a user. So in this example, 260 bytes is assumed.
#include<stdio.h>
void main()
{
void mystrrev(char *);
char str[100];
char *p1;
p1=str;
printf("Enter the string..?\n");
scanf("%s",str);
mystrrev(p1);
printf("Reverse is =%s",p1);
}
void mystrrev(char *p1)
{
char rev[100];
char *r;
r=rev;
int i=-1,j=0;
while(*p1!='\0')
{
p1++;
i++;
}
while(i>=0)
{
p1--;
*r=*p1;
r++;
j++;
i--;
}
*p1='\0';
*r='\0';
while(j-1>=0)
{
r--;
j--;
}
while(*r!='\0')
{
*p1=*r;
p1++;
r++;
}
*p1='\0';
}
simple code