I created a function to store a string in an array without spaces and punctuation:
int main()
{
char arr[1];int b,i=0;
bool newl = false;
for(;!newl;)
{
arr[i]=cin.get();
b = arr[i];
if(b>=65&&b<=90) i++;
else if(b>=97&&b<=122) i++;
if(arr[i]=='\n') newl =true;
}
for(int j=0;j<i;j++)
cout << arr[j];
}
it seemed pretty logic to me but when i tested it, its behaviour didnt turn out as i expected like with 1 character its ok but more than that its just really wrong.Is it because of the cin.get? Sorry im newb.
Thanks.
You allocated only one element to arr, so accessing arr[1] or further is forbidden.
std::vector is useful as variable-length array.
Also I suggest you should use isalpha() from library cctype instead of the comparation against magic numbers that are relatively hard to understand and dependent on the character code.
#include <iostream>
#include <vector>
#include <cctype>
using std::cin;
using std::cout;
int main()
{
std::vector<char> arr;int b,i=0;
bool newl = false;
for(;!newl;)
{
b = cin.get(); // store the input directly into b
if(isalpha(b)) arr.push_back(b);
if(b=='\n') newl = true;
}
for(size_t j=0;j<arr.size();j++)
cout << arr[j];
}
Related
I am trying to create a function that prints the elements of an array. I set it up so it calculates the size of the array, but I cannot figure why it doesn't work. Can you give me some suggestions?
Thanks!
#include <iostream>
#include <string>
using namespace std;
void print_array(string s){
for(int i = 0; i < ( sizeof(s) / sizeof(s[0]) ); i++){
cout << s[i] << "\n";
}
}
int main()
{
string names[5] = {"Dante", "Greg", "Bob", "Victor", "Saber"};
print_array(names);
}
Welcome to Stack Overflow! Be aware that there are many questions similar to this that have received answers.
As mentioned in a comment, you would need to specify the size of the array if you plan on passing it into a function, because the compiler will look at it not as an array of strings (string s[]), but as a pointer to strings (string s*). Thus, you would need to modify it a little like so:
#include <iostream>
#include <string>
using namespace std;
void print_array(string s[], int size){
for(int i = 0; i < size; i++)
{
cout << s[i] << "\n";
}
}
int main()
{
string names[5] = {"Dante", "Greg", "Bob", "Victor", "Saber"};
print_array(names, sizeof(names) / sizeof(names[0]));
}
You are passing a string instead of an array of strings. You could modify your code by using vectors like this:
void print_array(const std::vector<std::string> &vector){
for (const auto &string : vector) {
std::cout << string << "\n";
}
}
int main()
{
std::vector<std::string> names = {"Dante", "Greg", "Bob", "Victor", "Saber"};
print_array(names);
}
Using vectors allows you to use auto generated for loops, wich are easy to read and use.
I'm getting this error hence I am new to c++ I could not understand
please help me!!!
I am writing a palindrome code
This is the code given below:.............
I am basically here using some extra concepts not doing in-direct fashion.
if anyone can post the correct code he/she is most welcome...
//palindrome
#include <cstring> //or use #include <string.h>
#include <iostream>
using namespace std;
void Palindrom(string& );
void Palindrome(string& word)// same as (const string& word)
{
int n = word.length();
string word2;
char reverse[n];
for(int i = 0; i <=n; i++){
word[i]=tolower(word[i]);
}
word2=word; //now both are small
for(int i = n-1; i >=0; i--){
reverse[n-1-i]=word2[i];
cout<<reverse[n-1-i];
}
for(int i =0; i >n; i++){ //printing reversed
cout<< " Reverse: "<<reverse[i]<<endl;
}
// word is ok and word2 gets reversed
for (int i = 0; i <= n; i++){
if(word[i]==reverse[i])
{
cout<<"\nit is palandrome ";
}
cout<<"\nit is not a palindrome ";
}
}
int main()
{ string k="YuUuy";
void Palindrome(k);
return 0;
}
Correct syntax for calling a function is Palindrome(k); without the void.
Few remarks:
Get a good c++
book.
// same as (const string& word) is not true.
You did not include <string> header.
It's good practice to use std::size_t for indices, but beware of unsigned>=0 condition being always true.
char reverse[n]; is wrong, n must be a compile-time constant, VLA are not part of the C++ standard.
Function calls should not have return type. Change void Palindrome(k); in main() function to Palindrome(k);
While declaring array, the expression should have constant value. So you can't use char reverse[n];. Change it to char *reverse = new char[n]; and deallocate it using delete[] reverse; after you are done using it.
I would recommend you to use smart pointer. You should also take a look at std::string instead of using stream of char.
I am creating a program that scans user input for words that are listed in an array. The find() function seems like it'll work, but I can't find anything showing how to implement it for what I want to do. I'm pretty new to programming (obviously).
#include <iostream>
#include <time.h>
#include <stdlib.h>
#include <string>
#include <vector>
#include <algorithm>
using namespace std;
string subj [5]={"I","He","She","We","They"};
string verb [5]={" like"," hate"," sacrifice"," smell"," eat"};
string obj [5]={" bacon","s cats","s bagels","s children","s cops"};
string greeting [5]={"How are you","How's it going","Sup dude","Hey","Hello"};
string negvibe [4]={"bad","terrible","lousy","meh"};
string userfeeling;
int main()
{
srand(time(0));
int rando = rand() %5;//generates a random number between 0 and 4
int rando1 = rand() %5;
int rando2 = rand() %5;
cout << greeting [rando1] << "." << endl;
getline(std::cin,userfeeling);
if .... // What has to be done here?
find(negvibe, negvibe + 4, userfeeling) != negvibe + 4);
// Something like that?
// then ...
{
cout << subj[rando] << verb[rando1] << obj[rando2] <<"." <<endl;
}
return 0;
}
To make find work properly you should user iterators like so
if(find(std::begin(negvibe), std::end(negvibe), userfeeling) != std::end(negvibe)){
//code you want to happen if your word is found
}
Also in your current code, the if statement doesnt actually do anything since you end it with a semicolon and not {} or leave it blank if its one line. You can see an example of the if statement as well
Below is a link to find and iterators
http://www.cplusplus.com/reference/algorithm/find/
That find function will find some element of the negvibe array that is equal to userfeeling. If you are checking whether any element of negvibe is a substring of userfeeling, you should loop through negvibe and use the std::string::find method.
bool found_negvibe = false;
for (int i = 0; i < sizeof(negvibe) / sizeof(*negvibe); i++) {
found_negvibe = found_negvibe || userfeeling.find(negvibe[i]) != string::npos;
}
Also, you don't need to specify the size of the negvibe array, you can write this:
string negvibe[] = {"bad","terrible","lousy","meh"};
One more thing, you might prefer to use a std::vector over an array, if only because c++'s faculties for getting the size of a vector are slightly more succinct than those for getting the size of an array.
vector negvibe = {"bad","terrible","lousy","meh"};
bool found_negvibe = false;
for (int i = 0; i < negvibe.size(); i++) {
found_negvibe = found_negvibe || userfeeling.find(negvibe[i]) != string::npos;
}
Hey I'm quite new to programming and I'm having trouble using the isalpha function in my programme. This a part of the code for a palindrome class. What I'm trying to do is remove all the non alphabetic characters from the input. So if the user inputs "Hi, How are you" I need to first count the size of the array of just the letters then in my removeNonLetters subclass, I need to get rid of the non alphabetical characters. Can someone please help me with this. Thank you so much!
#include <iostream>
#include <string>
#include <stdio.h>
#include <algorithm>
#include <cctype>
#include <cstring>
#include <ctype.h>
using namespace std;
class palindrome
{
private:
int only_letters_size;
string input_phrase;
string* only_letters;
public:
string inputPhrase();
string removeNonLetters();
string* new_Array;
int size_new_Array;
};
string palindrome::inputPhrase()
{
cout << "Input phrase: "; //asks the user for the input
getline(cin,input_phrase);
size_new_Array = input_phrase.length(); //creating a dynamic array to store
the input phrase
new_Array = new string[size_new_Array];
int i;
for (i=0; i<size_new_Array; i++)
{
new_Array[i]=input_phrase[i];
}
only_letters_size = 0;
while(new_Array[i])
{
if (isalpha(new_Array[i])) //PROBLEM OCCURS HERE
{
only_letters_size=only_letters_size+1;
}
}
cout << only_letters_size << endl;
return new_Array;
}
string palindrome::removeNonLetters()
{
int j=0;
int str_length = new_Array.length(); //string length
only_letters = new string[only_letters_size];
for (int i=0;i<size_new_Array;i++) //PROBLEM OCCURS HERE AS WELL
{
if (isalpha(new_Array[i]))//a command that checks for characters
{
only_letters[j] = new_Array[i];//word without non alphabetical c
characters is stored to new variable
j++;
}
}
cout << only_letters << endl;
return only_letters;
}
I've found the best way to determine if a string is a palindrome is to walk toward the center from both sides. In your case I would just opt to skip non-alpha characters like so.
bool is_palindrome(string mystring)
{
int start = 0, end = mystring.length() - 1;
while (start < end)
{
// Skip over non-alpha characters
while (!isalpha(mystring[start]))
{
start++;
}
while (!isalpha(mystring[end]))
{
end--;
}
if (tolower(mystring[start]) != tolower(mystring[end]))
{
return false;
}
else
{
start++;
end--;
}
}
return true;
}
If you must save the input first and remove nonalpha characters, I would do it like this.
string remove_non_alpha(string mystring)
{
string ret_string = "";
for (int i = 0; i < mystring.length(); i++)
{
if (isalpha(mystring[i]))
{
ret_string += tolower(mystring[i]);
}
}
return ret_string;
}
And then feed the result into the above function.
Sorry for being hard, but your trying far too much copying around. You can achieve all this with one single loop after retrieving your data and all on one single string object (unless you want to keep the original input for some other purposes):
getline(cin,input_phrase);
std::string::iterator pos = input_phrase.begin();
for(char c : input_phrase)
{
if(isalpha(c))
{
*pos++ = tolower(c);
}
}
input_phrase.erase(pos, input_phrase.end());
After that, your string is ready to use...
Explanation:
std::string::iterator pos = input_phrase.begin();
An iterator something similar than a pointer to the internal data of the string. We keep the position to move the alpha only characters to, skipping the non-alpha ones.
for(char c : input_phrase)
Simply iterating over all characters...
if(isalpha(c))
The essential check, is the current character an alpha one?
*pos++ = tolower(c);
If so, convert it to lower case immediately. Assign it to the current string position, and advance the "pointer" (iterator!).
input_phrase.erase(pos, input_phrase.end());
And at very last, drop the remaining part of the string occupied with surplus characters. You might note that there might be some characters you wanted to keep within, but you copied these to a position more to the left already...
I am trying to do some array manipulations.
I am doing char array sorting and duplicates removal here.
Your comments are welcome. Havent done much testing and error handling here though.
#include<stdafx.h>
#include<stdlib.h>
#include<stdio.h>
#include<string>
using namespace std;
void sort(char *& arr)
{
char temp;
for(int i=0;i<strlen(arr);i++)
{
for(int j=i+1;j<strlen(arr);j++)
{
if(arr[i] > arr[j])
{
temp = arr[i];
arr[i] = arr[j];
arr[j] = temp;
}
}
}
}
bool ispresent(char *uniqueArr, char * arr)
{
bool isfound = false;
for(int i=0;i<strlen(arr);i++)
{
for(int j=0;j<=strlen(uniqueArr);j++)
{
if(arr[i]== uniqueArr[j])
{
isfound = true;
return isfound;
}
else
isfound = false;
}
}
return isfound;
}
char * removeduplicates(char *&arr)
{
char * uniqqueArr = strdup(""); // To make this char array modifiable
int index = 0;
bool dup = false;
while(*arr!=NULL)
{
dup = ispresent(uniqqueArr, arr);
if(dup == true)
{}//do nothing
else// copy the char to new char array.
{
uniqqueArr[index] = *arr;
index++;
}
arr++;
}
return uniqqueArr;
}
int main()
{
char *arr = strdup("saaangeetha");
// if strdup() is not used , access violation writing to
//location occurs at arr[i] = arr[j].
//This makes the constant string modifiable
sort(arr);
char * uniqueArr = removeduplicates(arr);
}
If you use std::string, your code (which is actually C-Style) can be written in C++ Style in just these lines:
#include <iostream>
#include <string>
#include <algorithm>
int main() {
std::string s= "saaangeetha";
std::sort(s.begin(), s.end());
std::string::iterator it = std::unique (s.begin(), s.end());
s.resize( it - s.begin());
std::cout << s ;
return 0;
}
Output: (all duplicates removed)
aeghnst
Demo : http://ideone.com/pHpPh
If you want char* at the end, then you can do this:
const char *uniqueChars = s.c_str(); //after removing the duplicates!
If I were doing it, I think I'd do the job quite a bit differently. If you can afford to ignore IBM mainframes, I'd do something like this:
unsigned long bitset = 0;
char *arr = "saaangeetha";
char *pos;
for (pos=arr; *pos; ++pos)
if (isalpha(*pos))
bitset |= 1 << (tolower(*pos)-'a');
This associates one bit in bitset with each possible letter. It then walks through the string and for each letter in the string, sets the associated bit in bitset. To print out the letters once you're done, you'd walk through bitset and print out the associated letter if that bit was set.
If you do care about IBM mainframes, you can add a small lookup table:
static char const *letters = "abcdefghijklkmnopqrstuvwxyz";
and use strchr to find the correct position for each letter.
Edit: If you're using C++ rather than C (as the tag said when I wrote what's above), you can simplify the code a bit at the expense of using some extra storage (and probably being minutely slower):
std::string arr = "saaangeetha";
std::set<char> letters((arr.begin()), arr.end());
std::copy(letters.begin(), letters.end(), std::ostream_iterator<char>(std::cout, " "));
Note, however, that while these appear the same for the test input, they can behave differently -- the previous version screens out anything but letters (and converts them all to lower case), but this distinguishes upper from lower case, and shows all non-alphabetic characters in the output as well.
char *arr = "saangeetha";
arr is pointing to read only section where string literal saangeetha is stored. So, it cannot be modified and is the reason for access violation error. Instead you need to do -
char arr[] = "sangeetha"; // Now, the string literal can be modified because a copy is made.