This is my first time asking something on stackoverflow, so I'm sorry if I fail in any aspect of building the topic etc...
So I'm a newbie at C++, I'm still at the beginning. I'm using a guide someone recommended me, and I'm stuck in a exercise which is about char and strings.
It's the following: They ask me to create a function that says the number of times that a certain word was repeated on a string.
I'll leave my code below for someone who can help me, if possible dont give me an obvious response like the code and then I just copy paste it. If you can just give me some hints on how to do it, I want to try to solve it on my own. Have a good night everyone.
#include <iostream>
#include <string.h>
#define MAX 50
using namespace std;
int times_occ(string s, string k) {
int count = 0, i = 0;
char word[sizeof(s)];
// while (s[i] == k[i])
// {
// i++;
// if (s[i] == '\0')
// {
// break;
// }
// }
for (i = 0; i <= sizeof(s); i++) {
if (s[i] == ' ' || s[i] == '\0') {
break;
}
word[i] = s[i];
}
word[i] = '\0';
for (i = 0; i <= sizeof(k); i++) {
if (word) {
if (k[i] == word[a]) {
a++;
count++;
}
}
}
cout << word << endl;
cout << count << endl; // this was supposed to count the number of times
// certain word was said in a string.
return count;
}
int main() {
char phrase[MAX];
char phrase1[MAX];
cin.getline(phrase, MAX);
cin.getline(phrase, MAX);
times_occ(phrase, phrase1);
}
Okay, first of all, the way you've used sizeof isn't really valid.
sizeof won't tell you the length of a string. For that, you want std::string::size() instead.
In this case, std::string is an object of some class, and sizeof will tell you the size of an object of that class. Every object of that type will yield the same size, regardless of the length of the string.
For example, consider code like this:
std::string foo("123456789");
std::string bar("12345");
std::cout << sizeof(foo) << "\t" << foo.size() << "\n";
std::cout << sizeof(bar) << "\t" << bar.size() << "\n";
When I run this, I get output like this:
8 9
8 5
So on this implementation, sizeof(string) is always 8, but some_string.size() tells us the actual length of the string.
So, that should at least be enough to get you started moving in a useful direction.
As #JerryCoffin mentioned, your word array has an invalid size. But - I want to make a more fundamental point:
Your code has two loops and a bunch of variables with arbitrary names. How should I know what's the difference between s and k? I even get k and i mixed up in the sense of forgetting that k is a string, not an integer. That kind of code difficult to read, and to debug. And we are a bit lazy and don't like debugging other people's code...
I suggest that you:
Have a very clear idea what your loops do, or what the different parts of your function do.
Create small self-contained functions - no more than one loop each please! - for each of those parts.
Use meaningful names for each function's parameters and for the local variables.
And then, if your program doesn't work - try debugging one function at a time.
Related
I picked up a challenge on r/dailyprogrammer on reddit which wants me to match a necklace and put the last letter at the beginning of a string. I've considered using nested for loops for this but this has made me really confused.
Instead I chose the way of replacing the last with the first character in an if-statement. But I am not getting my desired output with it, though I've tried everything what comes into my mind.
I used even std::swap() which didn't lead me to success either.
Here's the code:
#include <iostream>
#include <string>
#include <algorithm>
using namespace std;
string same_necklace(string& sInput, string& sOutput)
{
for (string::size_type i = 0; i < sInput.size(); i++)
{
if (sInput[i] == sInput.size())
{
sInput[0] = sInput[sInput.size()];
}
}
for (string::size_type j = 0; j < sOutput.size(); j++)
{
if (sOutput[j] == sOutput.size() - 1)
{
sOutput[0] = sOutput[sOutput.size()];
}
}
return sInput, sOutput;
}
int main()
{
system("color 2");
string sName{ "" };
string sExpectedOutput{ "" };
cout << "Enter a name: ";
cin >> sName;
cout << "Enter expected output: ";
cin >> sExpectedOutput;
cout << "Result: " << same_necklace(sName , sExpectedOutput) << endl;
return 0;
}
And of course the link to my challenge (don't worry, it's just Reddit!):
https://www.reddit.com/r/dailyprogrammer/comments/ffxabb/20200309_challenge_383_easy_necklace_matching/
While I am waiting (hopefully) for a nice response, I will keep on trying to solve my problem.
In your if you compare the value of the current index (inside the loop) with the size of the string. Those are two unrelated things.
Also, you use a loop though you only want to do something on a single, previously known index.
for (string::size_type i = 0; i < sInput.size(); i++)
{
if (sInput[i] == sInput.size())
{
sInput[0] = sInput[sInput.size()];
}
}
You could change the if condition like this to achieve your goal:
if (i == sInput.size()-1) /* size as the index is one too high to be legal */
But what is sufficient and more elegant is to drop the if and the loop. completely
/* no loop for (string::size_type i = 0; i < sInput.size(); i++)
{ */
/* no if (sInput[i] == sInput.size())
{*/
sInput[0] = sInput[sInput.size()-1]; /* fix the index*/
/* }
} */
I.e.
sInput[0] = sInput[sInput.size()-1]; /* fix the index*/
Same for he output, though you got the correct index already correct there.
This is not intended to solve the challenge which you linked externally,
if you want that you need to describe the challenge completely and directly here.
I.e. this only fixes your code, according to the desription you provide here in the body of your question,
"put the last letter at the beginning of a string".
It does not "switch" or swap first and last. If you want that please find the code you recently wrote (surely, during your quest for learning programming) which swaps the value of two variables. Adapt that code to the two indexes (first and last, 0 and size-1) and it will do the swapping.
So much for the loops and ifs, but there is more wrong in your code.
This
return sInput, sOutput;
does not do what you expect. Read up on the , operator, the comma-operator.
Its result is the second of the two expressions, while the first one is only valuated for side effects.
This means that this
cout << "Result: " << same_necklace(sName , sExpectedOutput) << endl;
will only output the modified sExpectedOutput.
If you want to output both, the modified input and the modified output, then you can simply
cout << "Result: " << sName << " " << sExpectedOutput << endl;
because both have been given as reference to the function and hence both contain the changes the function made.
This also might not answer the challenge, but it explains your misunderstandings and you will be able to adapt to the challenge now.
You have not understand the problem i guess.
Here you need to compare two strings that can be made from neckless characters.
Lets say you have neckless four latters word is nose.
Combination is possible
1)nose
2)osen
3)seno
4)enos
your function (same_necklace) should be able to tell that these strings are belongs to same necklace
if you give any two strings as inputs to your function same_necklace
your function should return true.
if you give one input string from above group and second input string from other random word thats not belongs to above group, your function should return false.
In that sense, you just take your first string as neckless string and compare other string with all possible combination of first string.
just move move you first latter of first input string to end and then compare each resulting string to second input string.
below is the function which you can use
void swap_character(string &test)
{
int length = test.length();
test.insert(length, 1, test[0]);
test.erase(0, 1);
}
So I am still new to C++, and I'm trying to make a program that has the user input a string, and then my functions return the string in reverse case, all lower case, and then all uppercase. Instead I just keep receiving the first letter of the string back, always uppercase. Not sure what I am doing wrong. Any suggestions?
#include <iostream>
#include <string>
#include <cstring>
using namespace std;
char answer[255] = "";
int max = strlen(answer);
void reverse() {
for (int i = 0; i < max; i++) {
if (islower(answer[i])) {
isupper(answer[i]);
}
else if (isupper(answer[i])) {
islower(answer[i]);
}
else if (isspace(answer[i])) {
isspace(answer[i]);
}
}
cout << answer[max];
}
void lower() {
for (int i = 0; i < max; i++) {
if (isupper(answer[i])) {
islower(answer[i]);
}
else {
answer[i] = answer[i];
}
}
cout << answer[max];
}
void upper() {
for (int i = 0; i < max; i++) {
if (islower(answer[i])) {
isupper(answer[i]);
}
else {
answer[i] = answer[i];
}
}
cout << answer[max];
}
int main() {
cout << "Please enter a word, or a series of words: " << endl;
cin >> answer[max];
reverse();
lower();
upper();
system("pause");
return 0;
}
islower(char) is just a built in function to check if the char is in lowercase or not. Same goes with isupper. It does not change the case of the character.
In order to convert to lowercase/uppercase, use tolower/toupper. This would return the character in the converted case. But, it is important that you need to assign the returned value to the character itself.
Refer to this answer for some more clarity related to islower, isupper, tolower and toupper.
And now coming to the point why it's printing just the 1st character: As #user4581301 has mentioned in his comment,
"cin >> answer[max]; will read exactly one character because answer[max] is exactly one character, the first character. In C++ you have to do things in order. For example, int max = strlen(answer); will provide an answer based on what is in that string at that time. Since the string was initialized one line earlier and contains an empty string, max will be 0."
Hence your cin should be cin >> answer. BUT, this will accept the 1st word of your sentence. In order to accept all the words including the spaces, use getline() instead. And for using this, answer should be declared as string answer instead of a char array.
This is how you accept a full sentence: getline(cin,answer);
And your variable max will give an error in a few compilers as being ambiguous. This is because of the using namespace std;. to avoid this, rename max to something else, like maxlen.
And finding the length of answer: It would be better if you call answer.length() after accepting the string from user rather than doing it globally.
Your working code should look something like this:
#include <iostream>
#include <string>
#include <cstring>
using namespace std;
string answer;
int maxlen;
void reverse() {
for (int i = 0; i < maxlen; i++) {
if (islower(answer[i])) {
answer[i] = toupper(answer[i]);
}
else if (isupper(answer[i])) {
answer[i] = tolower(answer[i]);
}
else if (isspace(answer[i])) {
answer[i]=' ';
}
}
cout << "Reversed string: " + answer << endl;
}
void lower() {
for (int i = 0; i < maxlen; i++) {
if (isupper(answer[i])) {
answer[i] = tolower(answer[i]);
}
else {
answer[i] = answer[i];
}
}
cout << "Lower case string: " + answer << endl;
}
void upper() {
for (int i = 0; i < maxlen; i++) {
if (islower(answer[i])) {
answer[i] = toupper(answer[i]);
}
else {
answer[i] = answer[i];
}
}
cout << "Upper case string: " + answer << endl;
}
int main() {
cout << "Please enter a word, or a series of words: " << endl;
getline(cin,answer);
cout << "Original string: " + answer << endl;
maxlen = answer.length();
reverse();
lower();
upper();
return 0;
}
With the output:
Please enter a word, or a series of words:
ReVeRsAl UPPER aNd lower
Original string: ReVeRsAl UPPER aNd lower
Reversed string: rEvErSaL upper AnD LOWER
Lower case string: reversal upper and lower
Upper case string: REVERSAL UPPER AND LOWER
cin >> answer[max];
will read exactly one character because answer[max] is exactly one character, the character in the array at position max.
max is 0 because you have to do things in order. For example,
int max = strlen(answer);
will provide the length of answer at that time this line is reached. Since the string was initialized one line earlier
char answer[255] = "";
and contains an empty string, max will be 0. This means answer[max] is answer[0] Nothing in the code ever changes max, so it will remain 0.
OK, say we change things a little and rather than reading into a single character, we read into answer as a string. You will need to
cin.getline(answer, sizeof(answer));
because
cin >> answer;
will read one whitespace-delimited token. One word. Your stated goal is to read more than one word. istream::getline will read everything it finds into the first parameter up to the end of the line or it finds the number of characters specified in the second parameter minus 1 (in order to reserve space for the string's null terminator). sizeof(answer) is literally the size of the answer array in bytes. We're operating in byte-sized characters so the count of characters and number of bytes are the same. Extra care must be taken if multibyte characters are being used.
This seems like a good place to recommend using std::string and std::getline instead. They make a large number of problems, such as the maximum number of characters that can be read, vanish for the vast majority of cases.
I'm not going to use them here, though because the assignment likely has a "No strings" policy.
So now that we have cin.getline(answer, sizeof(answer)); reading the user's input we can work on getting the size for max. We could strlen, but we could also use istream::gcount to get the number of characters read by getline.
main now looks something like
int main() {
cout << "Please enter a word, or a series of words: " << endl;
cin.getline(answer, sizeof(answer));
max = cin.gcount();
reverse();
lower();
upper();
system("pause");
return 0;
}
Whole bunch of stuff can go wrong at this point.
using namespace std; can wreak havoc on the max because of possible collisions with std::max. In general, avoid using namespace std; The few letters it saves you from typing often are recovered by the time wasted debugging the weird errors it can introduce.
isupper(answer[i]); doesn't do anything useful as others have noted in the comments. You want
answer[i] = toupper(static_cast<unsigned char>(answer[i]));
See Do I need to cast to unsigned char before calling toupper(), tolower(), et al.? for why that insane-and-pointless-looking cast may be necessary. Thank you HolyBlackCat for bringing that to my attention.
Self assignments like
answer[i] = answer[i];
are pointless for reasons that should be obvious once you stop and think about it.
Likewise
else if (isspace(answer[i])) {
isspace(answer[i]);
}
May not be particularly useful. If answer[i] is a space, set it to a space? It's already a space. What it would do is replace other forms of whitespace, tabs and carriage returns, with a space. Newline has already been picked off by getline. Also probably needs a cast similar to the one used in the toupper example above. I'm still reading up on that.
As hinted at above,
cout << answer[max];
is not effective. It prints out one character, and if max has been fixed, answer[max] will be the terminating null. Instead print out the whole array.
cout << answer;
General suggestions:
Don't write much code at a time. Write a few lines, a function at the most, before compiling and testing. If you had tested
int main() {
cout << "Please enter a word, or a series of words: " << endl;
cin >> answer[max];
cout << answer;
}
You would have immediately seen data was not being read correctly. and fixed it before proceeding. By allowing errors to build up, you make it harder to find any one bug. You may correctly fix a bug only to find the fix undone or concealed by another bug.
Avoid using global variables. Try to place variables in the smallest possible scope. In this case, move answer and max into main and pass them to the other functions as parameters. This makes it a lot easier to keep track of who set what variable and when. It also helps prevent accidental Variable Shadowing.
I am passing a string to my function, and the function is supposed to use that string to put individual chars in a stack. Then the stack is supposed to spit it back out (Since it's a stack it should be reversed). For example if my string is hello, it should print "olleh". But instead I'm getting ooooo. I think it has something to do with the fact that I'm setting ch equal to a different character every time but I'm not sure how to input those character in a different way.
void Stack::function2reverse(string myString) {
int countItIt = 0;
int sizeOfString = myString.size();
char Ch ;
for (int i= 0; i< sizeOfString; x++)
{
Ch = myString[x];
stack.push(Ch);
countIt ++;
}
while (countIt != 0)
{
cout << Ch;
stack.pop();
countIt --;
}
}
cout << Ch; - you print the same character every time (the last one entered, so 'o').
Instead, print the top character in the stack: std::cout << stack.top().
std::stack keeps track of its own size, so you don't need to worry about that either. Then you can replace your print loop with:
while (!stack.empty()) {
std::cout << stack.top();
stack.pop();
}
And of course, the Standard Library provides a std::reverse function anyway, so if this was not just an exercise in learning about std::stack, you could use that (and I can think of several other things to do as well, depending on exactly what you are trying to achieve):
std::string s = "hello";
std::reverse(std::begin(s), std::end(s));
// s now contains "olleh"
You may also want to read up on why using namespace std; is a bad practice.
I want to cout my string, everything works as it should, but when the string is shown, it immediately shows me the "example_4578.exe has stopped running" error. I have noticed that the problem is in the i < str[32].length part, because when I change it to i < 3, it works without any problem. How should I solve this?
std::string str[32];
cin >> str[1];
cout << "str[1]=" << str[1] << endl;
cin >> str[2];
cout << "str[2]=" << str[2] << endl;
for (int i = 0; i < str[32].length; i++)
{
cout << str[i];
}
EDIT 1.
I've made a huge mistake. I actually want to find the "number" of elements/words in "str". In my example, I have only designed two cins. But I actually want to design a "for" loop later on, so that the user can input as many words as he wants, so if he inputs 4 words, I want that code to return those number of words to me. How should I do this? In other words, how can I find out how many elements are in "str"?
Couple of things:
C++ is 0-indexed. What this means is that std::string str[32] has indices that go from 0 to 31, and str[32] should not be accessed. This will cause a crash.
str[31].length() (which is presumably what you wanted) is the length of the last string, not the length of the array. The length of the array is 32, and your loop should read for(int i = 0; i < 32; i++).
The main problem is that you are accessing an element (number 32) that is out of the bounds (0 - 31). To solve this problem and not repeat it again in the future use a range-for loop:
std::string str[32];
for (auto s : str)
std::cout << s;
str[32].length is not what you think.
I guess you meant somthing like: length of a 32-elements array. Right?
What you've written is pointer to funciton length of 33rd element of array.
This is because the types are:
std::string str[32]; // `str` is 32-element array of `std::strings`
str[32]; // `std::string` taken from 33rd position in array `str` (arrays' indexing starts at 0)
std::string has a member function named size_t std::string::length(). When referenced by name, you get its address.
To achieve what you wanted, you'd need to write:
for (int i = 0; i < 32; i++) {
cout << str[i];
}
Unfortunately, plain arrays don't have length (or anything similar) built in. So, you'd either need to use a constant, or (better) use a container, such as std::vector.
I'm working on a project where I need to have the computer print the 12 days of Christmas lyrics. I thought of an idea where I make a FOR loop and have it repeat 12 times. Every time the day changes with the unary operator "++" Here's what I mean:
int main()
{
string Print = first = 1; //Here I want first to become a number so that I can call it up in FOR loop.
cout << "On the first day of Christmas, \nmy true love sent to me\nA partridge in a pear tree.\n" << endl;
for(int loop = 0; loop <= 12; loop++)//This part is a simple for loop, it starts at 0 and goes to 12 until it stops.
{
cout << "On the " << (1,2,3,4,5,6,7,8,9...12) << " day of Christmas,\nmy true love sent to me\n" << endl; HERE!!!!
Here is where I'm having issue. I want the numbers to call in strings to say the day. As in x = 1 will call in "First" and then I can move the number up by using "x++" which will result in x = 2 and then it will say "Second".. all the way to 12. Anyone know how I can resolve this issue?
}
This involves a simple but important part of programming called an array. I don't want to give you the answer directly - you need to use these (or similar structures) all the time, and it is very important to practice their use and understand them. Let's make a simple program using arrays that prints "Hello World":
#include <iostream>
#include <string>
int main() {
std::string words[2]; //make an array to hold our words
words[0] = "Hello"; //set the first word (at index 0)
words[1] = "World"; //set the second word (at index 1)
int numWords = 2; //make sure we know the number of words!
//print each word on a new line using a loop
for(int i = 0; i < numWords; ++i)
{
std::cout << words[i] << '\n';
}
return 0;
}
You should be able to figure out how to use a similar tactic to get the functionality you asked for above. Working Ideone here.