I want to replace a pair of characters with another pair.
For example if want to replace "ax" with "57" and the string is "vksax", it will give out "vks57".
Tried it this way but get a weird output that is only partially correct:
#include <stdio.h>
#include <stdlib.h>
int main()
{
char dummy;
int i;
char string[16];
scanf("%s", string);
for(i=0;string[i];i++){
if(string[i] == 'a' && string[i+1] == 'x'){
string[i] = '5' ;
string[i+1] = '7';
i=0;
}
printf("%s", string) ;
}
exit(0);
}
I can't figure out why it gives, for example, with an input of 1234ax the output 1234ax1234ax1234ax1234ax123457123457123457123457123457123457
Within the for loop
for(i=0;string[i];i++){
if(string[i] == 'a' && string[i+1] == 'x'){
string[i] = '5' ;
string[i+1] = '7';
i=0;
}
this statement
i=0;
does not make a sense. Remove it. And instead of
string[i+1] = '7';
write
string[++i] = '7';
And move this call
printf("%s", string) ;
outside the for loop.
Pay attention to that the variable dummy is declared but not used.
char dummy;
Remove this declaration.
And there is no great sense to use exit( 0 ); instead of return 0;.
And the call of scanf will be more safer if to write it like
scanf("%15s", string);
Since this question is marked as C++, here is C++ one-line answer:
#include <string>
std::string String = "vksax";
String.replace(String.find("ax"), 2, "57");
Get yourself familiar with std::string
https://www.cplusplus.com/reference/string/string/
Solution as function(it assumes substring to be replaced and replacement have the same length):
std::string FindAndReplace(std::string sInputString, std::string sReplaceThis, std::string sReplacement)
{
size_t iPos = sInputString.find(sReplaceThis);
if(iPos == std::string::npos)
return sInputString;
sInputString.replace(iPos, sReplacement.length(), sReplacement);
return sInputString;
};
Related
I have a small program that prints out the capital form of each letter of a word, but I get the error signed/unsigned mismatch when I compile it because I'm passing a cstring as a normal string in this program. How do I pass it correctly so that I can still use text.length()? Here is the error that I get "Tester.cpp(22,23): warning C4018: '<': signed/unsigned mismatch". It's at for (int i = 0; i < text.length(); i++)
#include <iostream>
using namespace std;
string capitalizeFirstLetter(string text);
int main() {
char sentence[100];
for ( ; ; )
{
cin.getline(sentence, 100);
if (sentence != "0")
capitalizeFirstLetter(sentence);
}
return 0;
}
string capitalizeFirstLetter(string text) {
for (int i = 0; i < text.length(); i++)
{
if (i == 0)
{
text[i] = toupper(text[i]);
}
if (text[i] == ' ')
{
++i;
text[i] = toupper(text[i]);
}
}
cout << text;
return text;
}
The simplest way to handle passing sentence as a string is to enclose it in a braced set, to provide direct initialization to the parameter std::string text eg..
for ( ; ; )
{
std::cin.getline(sentence, 100);
if (*sentence)
capitalizeFirstLetter({sentence});
}
This allows the character string sentence to be used as the Direct initialization to initialize std::string text in your capitalizeFirstLetter() function:
std::string capitalizeFirstLetter (std::string text) {
for (size_t i = 0; i < text.length(); i++)
{
if (i == 0)
{
text[i] = toupper(text[i]);
}
if (text[i] == ' ')
{
++i;
text[i] = toupper(text[i]);
}
}
std::cout << text;
return text;
}
Your complete code, after reading Why is “using namespace std;” considered bad practice?, would then be:
#include <iostream>
std::string capitalizeFirstLetter (std::string text) {
for (size_t i = 0; i < text.length(); i++)
{
if (i == 0)
{
text[i] = toupper(text[i]);
}
if (text[i] == ' ')
{
++i;
text[i] = toupper(text[i]);
}
}
std::cout << text;
return text;
}
int main (void) {
char sentence[100];
for ( ; ; )
{
std::cin.getline(sentence, 100);
if (*sentence)
capitalizeFirstLetter({sentence});
}
return 0;
}
(note: dereferencing sentence provides the first character which is then confirmed as something other than the nul-terminating character (ASCII 0))
A Better CapitalizeFirstLetter()
A slightly easier way to approach capitalization is to include <cctype> and an int to hold the last character read. Then the logic simply loops over each character and if the first character is an alpha-character, then capitalize it, otherwise only capitalize the letter when the current character is an alpha-character and the last character was whitespace, e.g.
std::string capitalizeFirstLetter (std::string text)
{
int last = 0
for (auto& c : text)
{
if (isalpha(c))
{
if (!i || isspace (last))
c = toupper(c);
}
last = c;
}
std::cout << text;
return text;
}
(note: the use of a range-based for loop above)
Either way works.
The error is not generating because of you passing a cstring as a normal string to the function but it is due to the fact that you are trying to compare c style string using != operator in the statement
if (sentence != "0")
capitalizeFirstLetter(sentence);
try using strcmp() for that
Several things bugging me here.
First off, don't use using namespace std, it's "ok" in this case, but don't get used to it, it can cause quite some trouble.
See Why is “using namespace std;” considered bad practice?
Next thing is, just use std::string instead of cstrings here, it's easier to write and to read and doesn't produce any measurable performance loss or something. And it's harder to produce bugs this way.
So just use
std::string sentence;
and
getline(std::cin, sentence);
And why do you handle the output inside the function that transforms your string? Just let the main print the transformed string.
So your main could look like this:
int main() {
std::string sentence;
while(true)
{
getline(std::cin, sentence);
auto capitalized = capitalizeFirstLetter(sentence);
std::cout << capitalized;
}
return 0;
}
PS: the 'error' you get is a warning, because you compare int i with text.length() which is of type size_t aka unsigned int or unsigned long int.
Problems with your code :
if (sentence != "0") : illegal comparison. If you want to break on getting 0 as input then try using strcmp (include <cstring>) as if (strcmp(sentence, "0"). (Note that strcmp returns 0 when two strings are equal.) Or simply do if (!(sentence[0] == '0' and sentence[1] == 0)). Moreover this condition should be accompanied with else break; to prevent the for loop from running forever.
for (int i = 0; i < text.length(); i++) : generates warning because of comparison between signed and unsigned types. Change data-type of i to string::size_type to prevent the warning.
<string> (for std::string) and <cctype> (for std::toupper) were not included.
Thanks to #john for pointing this out. Your code has undefined behaviour if last character of a string is a space. Add a check if i is still less than text.length() or not before using text[i].
Another case of error is when an space is there after 0. Move getline to condition of for to fix this. Now there will be no need to input a 0 to terminate program. Moreover, I recommend using while loop for this instead of for.
You may also need to print a newline to separate sentences. Moreover, I would prefer printing the modified sentence in the main() function using the returned string from capitalizeFirstLetter.
It doesn't matter much in short (beginner-level) codes, but avoid acquiring the habit of putting using namespace std; on the top of every code you write. Refer this.
Fixed code :
#include <cctype>
#include <cstring>
#include <iostream>
#include <string>
using namespace std;
string capitalizeFirstLetter(string text);
int main() {
char sentence[100];
while (cin.getline(sentence, 100))
cout << capitalizeFirstLetter(sentence) << '\n';
}
string capitalizeFirstLetter(string text) {
for (string::size_type i = 0; i < text.length(); i++) {
if (i == 0)
text[i] = toupper(text[i]);
if (text[i] == ' ')
if (++i < text.length())
text[i] = toupper(text[i]);
}
return text;
}
Sample Run :
Input :
hello world
foo bar
Output :
Hello World
Foo Bar
My Version (Requires C++20) :
#include <cctype>
#include <iostream>
#include <string>
auto capitalizeFirstLetter(std::string text) {
for (bool newWord = true; auto &&i : text) {
i = newWord ? std::toupper(i) : i;
newWord = std::isspace(i);
}
return text;
}
int main() {
std::string sentence;
while (std::getline(std::cin, sentence))
std::cout << capitalizeFirstLetter(sentence) << std::endl;
}
Sample Run
I was trying to solve a programming problem of some site and this one had the following statement:
Read a string and parse it as a number, char 'l' can be considered as number 1 and chars 'o' and 'O' can be considered as number 0, commas and spaces will be accepted in the input but ignored, if any other character is found then output error...
So... since there can be spaces in the lines, I used gets (the documentation says it removes the new line and puts a terminator)...
My sequence of IF test if it is a number, then if its an acceptable letter, then checks if it is not a comma or a space... And I found out that it was almost always entering in the last IF even though there wasn't any character that should lead it there so I changed the printf inside it to print the
printf("%d error", st[k]);
And it outputs 13: carriage return... I tried this compiler here
#include <cstdio>
#include <cstring>
#include <cstdlib>
int main()
{
char st[100];
char buf[100];
int k, i;
long long int num;
ops: while(gets(st))
{
for(k = i = 0; st[k]; k++)
if(st[k] >= '0' && st[k] <= '9')
buf[i++] = st[k];
else if(st[k] == 'o' || st[k] == 'O')
buf[i++] = '0';
else if(st[k] == 'l')
buf[i++] = '1';
else if(st[k] != ',' && st[k] != ' ')
{
printf("error\n");
goto ops;
}
// remaining code comes here...
}
The input sample had the following lilnes:
lo6
234,657
hi
,,,,,5,,5, 4
2200000000
00
Should I use other function to read instead?
Any suggestions on how to avoid this damn Carriage Return?
The statemente for the problem can be seen here if you want more detail
Thanks
EDIT:
I'm asking that because there seem to be a difference between the compiler I'm using and the compiler the website was using, once I submitted a code that wasn't generating the correct output on mine but I thought the code was correct... and it passed. Then after it, I tried the code on a linux virtual machine and also correct but my gcc on windows failed... some characters were completely away from where they should be
The thing is:
The preferred method of line input is getline. If you do not know the width of the input beforehand, getline will allocate space for you if you set the buffer pointer to NULL.
Since you indicate you have some experience in C, the following will show you how to step through an input string and parse it in the manner you want. While there are many ways to handle parsing strings, it is hard to beat assigning a pointer to the beginning of the string and then advancing down the string until you reach the null-terminating character (unsigned 0, or char '\0'). If you have any questions after looking it over, just ask:
#include <stdio.h>
#include <stdlib.h>
int main (int argc, char *argv[]) {
char *buffer = NULL;
size_t n = 0;
ssize_t len;
char *ptr = NULL;
char *output = NULL;
int idx = 0;
printf ("\nEnter your string below: ([ctrl + d] on blank line to end)\n");
while ((len = getline (&buffer, &n, stdin)) != -1) {
ptr = buffer;
idx = 0;
output = malloc (sizeof (char) * len);
while (*ptr != 0) {
if (*ptr >= 48 && *ptr <= 57) output [idx++] = *ptr;
if (*ptr == 'I') output [idx++] = '1';
if (*ptr == 'o' || *ptr == 'O') output [idx++] = '0';
ptr++;
}
output [idx] = 0;
printf ("\n valid output: %s\n\n", output);
free (output);
}
return 0;
}
output:
Enter your string below: ([ctrl + d] on blank line to end)
This sting has 12345 aeiou AEIOU,,,,,commas, and 99, to end.
valid output: 123450100990
Question - Given a string a '0', '1' and '?'. Generate all possible strings where you can replace '?' with '0' or '1' ?
For eg - Input - "0??"
Output - "000", "001", "010", "011".
I have written a simple program for it -
void gen(string& str, int index)
{
int i;
if(str.length() == index)
{
cout << str << endl;
return;
}
else
{
for(i=index; str[i]!='\0' && str[i]!='?';i++);
if(str[i] == '?')
{
str[i] ='0';
gen(str,i+1);
str[i] ='1';
gen(str,i+1);
}
}
return;
}
int main()
{
string s ="0??";
gen(s, 0);
return 0;
}
It is not working correctly....
BUT IF YOU REPLACE THE ARGUMENT IN void gen(String &, int) to
void gen(String, int)....
THEN IT WILL WORK CORRECTLY..
Can Anyone explain me please....
When you pass the string by reference, there is a single string that is operated on by all of the recursive calls to gen() - instead of each call to gen() working on its own local copy. Each recursive call to gen() modifies the (shared) string, removing all the '?' characters; when that call returns, there are no more '?' characters left to process so it simply terminates.
when you pass the string by value, each invocation of the gen() function gets its own local copy of the string; Any changes it makes to that string are thrown away and forgotten when the function returns to the previous level. In this case your logic is correct.
(There was also a bug which caused it to crash on my Windows machine until I fixed it: std::string is not null-terminated, so rather than checking for std[i] == '\0' you should do something like i < str.length().)
reference will maintain the value changed in the function call
after set str[1] ='0';
sub call: gen(str,2); will output combination: 000 001
reset str[1] ='1';
str is still 011
gen(str,i+1); output nothing
hope this piece of code can help
#include <string>
#include <iostream>
#include <stdio.h>
using namespace std;
void gen(string& str, int index)
{
int i;
if(str.length() == index)
{
cout << str << endl;
return;
}
else
{
for(i=index; str[i]!='\0' && str[i]!='?';i++);
if(str[i] == '?')
{
printf("before set pos %d to 0: %s\n",i,str.c_str());
str[i] ='0';
printf("after set pos %d to 0: %s\n",i,str.c_str());
gen(str,i+1);
printf("before set pos %d to 1: %s\n",i,str.c_str());
str[i] ='1';
printf("after set pos %d to 1: %s\n",i,str.c_str());
gen(str,i+1);
}
}
return;
}
int main()
{
string s ="0??";
gen(s, 0);
return 0;
}
it outputs：
One simple solution will be:
As each '?' should be replaced with 0 and 1, we can see that there will be '2 ** (number of ?)' such possible replacement in the string. Eg., if we have three '?' in the string there will be 8 such possible replacement and if we consider their numeric value, they will be 0,1,2...,7 and binary representation of which will be 000,001,002,....,111. Basically we should take the the numeric values and replace the '?'s with the bits from the numeric values.
I want to add '.' character besides another character in a string but I don't know how to do it ? is it possible?
#include <iostream>
#include <string.h>
using namespace std;
int main(int argc, char *argv[]) {
string input;
char dot='.';
cin>>input;
for(int i=0;i<input.length();i++)
{
if( input[i]>=65 && input[i]<=90)
{
input[i]=input[i]+32;
}
if( (input[i]=='a') || (input[i]=='e') || (input[i]=='i') || (input[i]=='o') || input[i]=='y' || input[i]=='u' )
{
input.erase(i,i+1);
}
input[i]+=dot;
}
cout<<input<<endl;
return 0;
}
From the cpluplus.com reference ( http://www.cplusplus.com/reference/string/string/insert/ )
// inserting into a string
#include <iostream>
#include <string>
using namespace std;
int main ()
{
string str="to be question";
string str2="the ";
string str3="or not to be";
string::iterator it;
// used in the same order as described above:
str.insert(6,str2); // to be (the )question
str.insert(6,str3,3,4); // to be (not )the question
str.insert(10,"that is cool",8); // to be not (that is )the question
str.insert(10,"to be "); // to be not (to be )that is the question
str.insert(15,1,':'); // to be not to be(:) that is the question
it = str.insert(str.begin()+5,','); // to be(,) not to be: that is the question
str.insert (str.end(),3,'.'); // to be, not to be: that is the question(...)
str.insert (it+2,str3.begin(),str3.begin()+3); // (or )
cout << str << endl;
return 0;
}
Also, check these links:
http://www.cplusplus.com/reference/string/string/
http://www.cplusplus.com/reference/string/string/append/
http://www.cplusplus.com/reference/string/string/push_back/
Before you try writing the code, you should write a detailed
specification of what it is supposed to do. With your code, I
can only guess: convert to lower case (naïvely, pretending that
you'll only encounter the 26 unaccented letters in ASCII), then
delete all vowels (again, very naïvely, since determining
whether something is a vowel or not is non-trivial, even in
English—consider the y in yet and day), and finally
inserting a dot after each character. The most obvious way of
doing that would be something like:
std::string results;
for ( std::string::const_iterator current = input.begin(),
end = input.end();
current != end;
++ current ) {
static std::string const vowels( "aeiouAEIOU" );
if ( std::find( vowels.begin(), vowels.end(), *current )
!= vowels.end() ) {
results.push_back(
tolower( static_cast<unsigned char>( *current ) ) );
}
results.push_back( '.' );
}
But again, I'm just guessing as to what you are trying to do.
Another alternative would be to use std::transform on the
initial string to make it all lower case. If you're doing this
sort of thing regularly, you'll have a ToLower functional
object; otherwise, it's probably too much of a bother to write
one just to be able to use std::transform once.
I’m assuming you want this input:
Hello world!
To give you this output:
h.ll. w.rld!
Rather than trying to modify the string in place, you can simply produce a new string as you go:
#include <cctype>
#include <iostream>
#include <string>
using namespace std;
int main(int argc, char *argv[]) {
string input;
getline(cin, input);
string output;
const string vowels = "aeiouy";
for (int i = 0; i < input.size(); ++i) {
const char c = tolower(input[i]);
if (vowels.find(c) != string::npos) {
output += '.';
} else {
output += c;
}
}
cout << output << '\n';
return 0;
}
Notes:
<cctype> is for toupper().
<string.h> is deprecated; use <string>.
Read whole lines with getline(); istream::operator>>() reads words.
Use tolower(), toupper(), &c. for character transformations. c + 32 doesn’t describe your intent.
When you need comparisons, c >= 'A' && c <= 'Z' will work; you don't need to use ASCII codes.
Use const for things that will not change.
I'm not sure how this old question got bumped back onto the current list, but after reviewing the answers, it looks like all will miss the mark if the input is more than a single word. From your comments, it appears you want to remove all vowels and place a '.' before the character immediately prior to where the removal occurred. Thus your example "tour" becomes ".t.r".
Drawing from the other answers, and shamelessly removing 'y' as from the list of vowels, you can do something similar to:
#include <iostream>
#include <string>
int main()
{
std::string input;
if (!getline (std::cin, input)) {
return 1;
}
size_t i = 0;
for (; input[i]; i++)
{
switch (input[i])
{
case 'A': /* case fall-through intentional */
case 'E':
case 'I':
case 'O':
case 'U':
case 'a':
case 'e':
case 'i':
case 'o':
case 'u':
{
size_t pos = input.find_first_not_of("AEIOUaeiou", i+1);
if (pos == std::string::npos) {
pos = input.length();
}
input.erase(i, pos-i);
if (pos - i > 1) {
input.insert(i, 1, '.');
}
input.insert(i-1, 1, '.');
break;
}
}
}
std::cout << input << '\n';
}
Example Use/Output
Your example:
$ ./bin/vowels-rm-mark
tour
.t.r
A longer example:
$ ./bin/vowels-rm-mark
My dog has fleas and my cat has none.
My .dg .hs f.l.s. nd my .ct .hs .n.n.
Based on your comments, it sounds like you want something like this:
#include <iostream>
#include <string>
#include <algorithm>
int main(int argc, char *argv[])
{
std::string input;
std::cin >> input;
std::transform (input.begin(), input.end(), input.begin(), tolower);
size_t i = 0;
while (i < input.length())
{
switch (input[i])
{
case 'a':
case 'e':
case 'i':
case 'o':
case 'y':
case 'u':
{
size_t pos = input.find_first_not_of("aeioyu", i+1);
if (pos == std::string::npos)
pos = input.length();
input.erase(i, pos-i);
break;
}
default:
{
input.insert(i, 1, '.'); // or: input.insert(i, ".");
i += 2;
break;
}
}
}
std::cout << input << std::endl;
return 0;
}
I have this simple problem that gets an input from the user using a function then checks if the input is 'equal' to the "password". However, strcmp would never return my desired value, and the culprit is somewhere in my loop that uses getch() to take each character separately and add them to the character array. I found this out by having printf display the character array. If I type in pass word, the function would display it as pass word ". I have no idea on why the closing double quote and a whitespace was included in the array right after the word I typed in. Any idea? Here's the code. Thanks.
#include <stdio.h>
#include <iostream>
#include <conio.h>
#include <string.h>
int validateUser();
int main()
{
for(int x = 0;x<2;x++)
{
if(validateUser())
{
system("cls");
printf("\n\n\t\t** Welcome **"); break;
}
else
{
system("cls");
printf("\n\n\t\tIntruder Alert!");
system("cls");
}
}
system("PAUSE>nul");
return 0;
}
int validateUser()
{
char password[9];
char validate[] = "pass word";
int ctr = 0, c;
printf("Enter password : ");
do
{
c = getch();
if(c == 32)
{
printf(" ");
password[ctr] = c;
}
if(c != 13 && c != 8 && c != 32 )
{
printf("*");
password[ctr] = c;
}
c++;
}while(c != 13);
return (!strcmp(password, validate));
}
Your char array password does not
have a terminating null char.
You need to ensure that you don't
stuff more than 8 char into
password
Also c++ should be ctr++
.
do {
// stuff char into password.
ctr++;
}while(c != 13 && ctr <8);
password[ctr] = 0;
You're incrementing c in your loop. You should be incrementing ctr. Also, all the stuff everyone else has said (null terminator, only 8 characters, etc).
getch() is a function defined in a non-standard header <conio.h>. Relying on non-standard features is not recommended when you want your code to be portable. :)
do {
// stuff char into password.
++ctr;
} while(c != 13 && ctr < 9);
password[ctr] = '\0';