I was attempting to print the first letter of each words in a sentence in C++. My idea was to print the first letter of a string first , then print every letter after a space:
#include <string.h>
#include <stdio.h>
#include <iostream>
using namespace std;
string sentence;
int main(int argc, char const *argv[])
{
cout << "Input your name!" << endl;
cin >> sentence;
//output first character
cout << sentence[0] << endl;
//output the rest of first characters in words
for(int i = 0; i < sentence.length(); i++){
if (sentence[i] == ' ' && sentence[i+1]!= '\0'){
cout << sentence[i+1]<< endl;
}
}
return 0;
}
This solution only printed the very first letter of the string , and I was having trouble determining what went wrong with my code.
std::cin will stop reading into a string after the first whitespace. So, if you input hello world, it will only read "hello" into your string. Instead, you can read an entire line into your string using std::getline:
cout << "Input your name!" << endl;
getline(cin, sentence);
...
Also, the contents of a std::string won't have a nul character ('\0') in it whichever method you use, so your sentence[i+1] != '\0' check won't ever stop you from printing something.
Related
I need to make a program which converts all letters to uppercase.
But first I need to get an input from the user. And I need to check if there are characters that are not space or alphabet.
This is what I tried.
#include <iostream>
#include <cctype>
using namespace std;
int main()
{
string s;
cout << "Enter a string: ";
while (getline(cin, s)){
for (int i = 0; i<s.length(); i++){
if ((isspace(s[i]) || isalpha(s[i]))){
for (int i = 0; i < s.length(); i++){
s[i] = toupper(s[i]);
}
cout << s << endl;
return 1;
}
cout << "Invalid string. Please input only alphabets or space character. " << endl << "Enter a string: ";
}
}
//if the input value is valid convert and print
return 0;}
This program successfully make error messages to pure numbers and pure question marks. But the problem is if there are invalid characters and valid characters mixed in the input, it cannot distinguish it.
For example, if input is "Hi?", the program thinks its a valid input. But with questions marks, the string should be invalid.
I think the for statement is the problem. How can I solve this?
I've made a few changes to deal with the break out conditions in your loops without changing the structure of your program too much.
Here's one example how you could get it to work. Comments in the code.
#include <cctype>
#include <iostream>
#include <string>
int main() {
std::string s;
while(std::cout << "Enter a string: " && std::getline(std::cin, s)) {
bool valid = true; // will stay true unless at least one char is invalid
for(char& ch : s) { // use a range-based for loop
// ch is now a reference to the char in the string
// convert to unsigned char - these functions are not safe
// otherwise:
if(std::isspace(static_cast<unsigned char>(ch)) ||
std::isalpha(static_cast<unsigned char>(ch)))
{
ch = std::toupper(static_cast<unsigned char>(ch));
continue; // continue to check the next character
}
std::cout << "Invalid character ('" << ch << "') in string.\n"
"Please input only alphabets or space character.\n";
valid = false; // to let the user enter a new string
break; // no need to check more characters, the string is invalid
}
if(valid) break; // break out only if all characters are valid
}
if(std::cin)
std::cout << "The valid string is now " << s << '\n';
}
A similar program could use algorithms from <algorithm> to do the check and the transformation of the string to uppercase.
Example:
#include <algorithm>
#include <cctype>
#include <iostream>
#include <string>
int main() {
std::string s;
// the manual loop replaced by a simple algorithm that checks if any
// character in the string is invalid by using a lambda, here called
// "is_invalid":
auto is_invalid = [](unsigned char ch) {
return !(std::isspace(ch) || std::isalpha(ch));
};
while(std::cout << "Enter a string: " &&
std::getline(std::cin, s) &&
std::any_of(s.begin(), s.end(), is_invalid))
{
std::cout << "Invalid character in string.\n"
"Please input only alphabets or space character.\n";
}
if(std::cin) {
// transform the valid string to uppercase using another lambda.
// the lambda is here only to make the chars into unsigned chars
// to make the use of std::toupper safe
auto to_upper = [](unsigned char ch) { return std::toupper(ch); };
std::transform(s.begin(), s.end(), s.begin(), to_upper);
std::cout << "The valid string is now " << s << '\n';
}
}
Write and test a program that prompts the user to input a file name and a string to test for. Search the file for every occurrence of the specified string – when the string is found, display the line that contains it. When all occurrences of the string have been found display the number of times the string appeared in the file. Hint: You may use string member function find().
Here's my code, as I stated it works with some sentences but not all, it doesn't seem to have anything to do with the length either as if I repeat a line I know works, it won't run into any errors, can someone explain?
#include <fstream>
#include <iostream>
#include <sstream>
#include <string>
#include <vector>
#include <cctype>
using namespace std;
void find_common_words(string, int);
vector<string> words;
int main(){
vector<string> line;
string input;
char filename[50];
ifstream inputFile;
cout << "Enter File Name:" << endl;
cin.getline(filename, 50);
inputFile.open(filename);
//TESTING IF FILE IS OPEN
if (!inputFile.is_open()){
cout << "File Wasn't Opened!" << endl;
return 0;
}
while (getline(inputFile, input)){
line.push_back(input);
}
int size_of_array = static_cast<int>(line.size());
for (int i = 0; i < size_of_array; i++){
istringstream iss(line[i]);
int word_number = 0;
do {
string word;
iss >> word;
words.push_back(word);
word_number++;
} while (iss);
}
string commonword;
cout << "Enter a word to search for (without punctuation)" << endl;
cin >> commonword;
int size_of_array2 = static_cast<int>(words.size());
find_common_words(commonword, size_of_array2);
return 0;
}
void find_common_words(string search, int sizeofarray2) {
//CONVERSION TO STRING WITHOUT PUNCTUATION
for (int i = 0; i < sizeofarray2; i++){
string temp_string = words[i];
for (int j = 0, len = temp_string.size(); j < len; j++){
if (ispunct(temp_string[j])){
temp_string.erase(j--, 1);
len = temp_string.size();
}
}
words[i] = temp_string;
}
//SEARCHING FOR SAME WORDS
int line_number = 1;
int words_found = 0;
for (int i = 0; i < sizeofarray2; i++){
if (search == words[i]){
cout << search << " Was found on line " << line_number << endl;
words_found++;
}
if (words[i].length() == 0){
line_number++;
}
}
cout << line_number - 1 << " lines checked, " << words_found << " matches " << endl;
}
Heres my input file (randomly generated):
It's a very big deal.
Carl won the spelling bee and got a trophy!
Why is your cat so big?
Do you have a big bowl I can borrow?
It's a big company.
Penguins live in the Antarctica.
Don’t be silly, you're going to the game!
What are you talking about?
He threw up in the trash can!
You're so ratchet!
But she is a good caretaker.
Tom is looking for a bigger house to live in.
I get an error with Debug Assertion
Expression c> = -1 && c < = 255
I debugged the program and WhozCraig is right. In your input text in the line
Don’t be silly, you're going to the game!
In the word "Don’t", you do not have the normal apostrophe as you have in the word "It's" or "you're"
This special character is encoded as -110 in temp_string. In the description of std::ispunct you can read:
The behavior is undefined if the value of ch is not representable as unsigned char and is not equal to EOF.
-110 does not fit and causes a debug assertion error. If you cast it to unsigned char like WhozCraig proposed, it will work.
You can also fix your input file.
A very interesting and subtle error . . .
The first character of cstring keeps being removed upon the second execution of getline in ifstream:
#include <iostream>
#include <fstream>
using namespace std;
int main(){
char input[102];
ifstream keyTextFile("key.txt");
while (keyTextFile.getline(input, 102, '\n')) {
cout << input[0] << input[1] << endl;
cout << input << endl;
}
cout << input[0] << input[1] << endl;
keyTextFile.close();
return 0;
}
Currently, key.txt is one line:
0x0ffa331cc8765ddd
The code outputs:
0x
0x0ffa331cc8765ddd
x
The debugger shows input[0] changing from '0' to '\0' on the second execution of getline. How can I avoid this while allowing getline to scan a potentially large document?
please keep the answer to c-string implementation.
The purpose of the program is to read a phrase from a file into a vector and convert the phrase into Pig Latin. When the translated phrase is outputted in Pig Latin, an additional "ay" is added after the phrase (which is not supposed to happen). Can anyone spot why this is happening? It is important that I fix this because it affects the total letters and total characters of the Pig Latin phrase that I need to output. Also, I'm not asking anyone to write any code for me, but any tips on how to make my code less redundant. A portion of my grade for programs is efficiency, which I usually lose points on.
Here's the code:
#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>
#include <sstream>
#include <cctype>
#include <stdio.h>
#include <ctype.h>
using namespace std;
int main()
{
ifstream in;
string word, fileName;
vector <string> phrase;
int length = 0, index = 0;
int totalWords = -1, totalLetters = -3, totalChars;
cout << "PIG LATIN PROGRAM" << endl;
cout << "Which file are you accessing? : ";
cin >> fileName;
fileName += ".txt";
in.open(fileName);
if (in.fail()) cout << "\nFile not found!" << endl;
while(getline(in, word)) phrase.push_back(word);
cout << "Original Phrase: " << phrase[0] << endl;
istringstream iss(phrase[0]);
cout << "Pig Latin phrase: ";
do {
string OGword;
string PLword;
for (int i=0; i < phrase.size(); i++){
iss >> OGword;
totalWords++;
}
if (OGword[0]=='a' || OGword[0]=='A' || OGword[0]=='e' || OGword[0]=='E' || OGword[0]=='i' || OGword[0]=='I' || OGword[0]=='o' || OGword[0]=='O' || OGword[0]=='u' || OGword[0]=='U'){
cout << OGword << "way" << " ";
totalLetters += (OGword.size() + 3);
}
else {
PLword = OGword.substr(index);
length = PLword.length();
PLword.insert(length, "ay");
PLword.insert(length, 1, OGword[index]);
PLword.erase(0, 1);
if (isupper(OGword[0])){
transform(PLword.begin(), PLword.end(), PLword.begin(), ::tolower);
(toupper(PLword[1]));
char upper;
upper = toupper(PLword[0]);
PLword.erase(0, 1);
cout << upper;
}
cout << PLword << " ";
totalLetters += PLword.size();
}
} while (iss);
totalChars = totalLetters + 1;
cout << "\n\nTotal words: " << totalWords << endl;
cout << "Total Letters: " << totalLetters << endl;
cout << "Total Characters: "<< totalChars << endl;
}
Problem
The core loop of the program looks like this (in pseudocode):
istringstream iss; // Contains line of text.
do {
string OGword;
get_OGword_and_count_totalWords(iss, OGword);
print_pig_latin_of_word(OGword);
} while (iss);
The loop runs as long as iss has not experienced an error. And in particular, iss does not experience an error until an extraction operation fails. So things happen in the loop like this:
OGword contains the last legitimate word on the line.
Print the last word.
The while clause is tested. iss is still good at this point because no error has occurred, even if iss is at the end of string.
Attempt to extract a word into OGword. This fails, and leaves OGword empty ("").
Print the Pig Latin version of "", which is "ay".
The while clause is tested. iss is in an error state, and the loop ends.
Fix
One possible fix out of many is to test iss for an error immediately after extracting a word.
std::istringstream iss; // Contains line of text
std::string OGword;
while (iss >> OGword) {
increment_word_total();
print_pig_latin_of_word(OGword);
}
In this version, the operation iss >> OGword returns iss, which is converted to bool. If there was an error during the immediately preceeding extraction, the loop ends without printing anything.
Other Advice
I think the best way to improve readability is to break the code up into smaller functions. For instance, take the if / else block that formats and prints the Pig Latin, and actually put it in a function:
int print_pig_latin_of_word_and_return_total_letters(string_view word);
Then, the code in that function can be further subdivided:
bool starts_with_vowel(std::string_view word);
int print_vowel_word_and_count_letters(std::string_view word);
int print_consonant_word_and_count_letters(std::string_view word);
int print_pig_latin_of_word_and_count_letters(std::string_view word) {
if (starts_with_vowel(word)) {
return print_vowel_word_and_count_letters(word);
} else {
return print_consonant_word_and_count_letters(word);
}
}
Odds and Ends
I would drop using namespace std and write all of the std library names as std::string, etc. This makes it clear which things are from the standard library.
The program has interesting behavior on input files that contain more than one line. There is a for loop that loops over phrase.size() which is number of input lines. This causes words to be skipped and totalWords to be incorrect.
This statement doesn't do anything, because the result of toupper is ignored:
(toupper(PLword[1]));
I'm working on homework for my c++ class, and it's been quite awhile since I've used it. I was wondering if there was a way to allow spaces in a string (instead of it nulling out and ending the string)
my current code is this:
int chapter10() {
string strinput;
char charstr[1000];
int numwords=1;
cout << "Enter a phrase ";
cin >> strinput;
cout << strinput;
const int size = strinput.size() + 1;
strcpy_s(charstr, strinput.c_str());
cout << strinput << endl;
for (int i = 0; i != size; i++) {
if (*(charstr + i) == ' ')
numwords++;
}
cout << "There are " << numwords << " words in that string." << endl;
return 0;
}
The problem I'm having, is for instance, if I type "Hello World" and press enter, it pops the next line (right after the cin) and says "Hello", and the space made it cut the rest of the phrase off.
How does one fix this issue? I don't want to use the str:: things as I barely know what they are, and have really never had to use them, and that would look a bit suspicious to the teacher :P
Update: If you've suggested using getline(cin, strinput); It doesn't work too well. I can from what I see, only type in the 10 to reach my function, but after I press enter, it thinks that I've presses something else, which makes it completely skip the cin to get the string value. But, there is something weird with this, if I type "10 hello world" it does everything correctly. Well, with the exception that it needs to be in the same line as the number to reach the function.
Solved: The use of getline(cin, strinput) works perfectly fine, if you're not using user input before hand. If you are, you're going to need a cin.ignore before the getline(). As stated in the comment by my best answer.
#include <iostream>
#include <iomanip>
#include <string>
#include <limits>
using namespace std;
//~~~Initialize all functions
int chapter10();
//~~~Initializing complete
int main() {
srand(time(0)); //makes rng thingy work instead of choose same numbers cause it doesn't do it on its own. lol
cout << "Enter the chapter number you need to look at: ";
int chapterNumber;
cin >> chapterNumber;
switch (chapterNumber) {
case 1: testingStuff(); break;
case 9: chapter9(); break;
case 10: chapter10(); break;
default: cout << "You chose an invalid chapter number, reload the program."; break;
}
system("pause");//So console doesn't close instantly cause that's not annoying at all...
}
int chapter10() {
string strinput;
char charstr[10000];
int numwords=1;
cout << "Enter a phrase." << endl;
cin.ignore(numeric_limits<streamsize>::max(), '\n');
getline(cin, strinput);
const int size = strinput.size() + 1;
strcpy_s(charstr, strinput.c_str());
for (int i = 0; i != size; i++) {
if (*(charstr + i) == ' ' & *(charstr + (i+1)) != ' ' )//the & is fail safe so multiple space no ++numwords
numwords++;
}
cout << "There are " << numwords << " words in that string." << endl;
return 0;
}
The way I have my code written was I used a switch/case to reach my function. This required user input, which in turn caused my program to 'think' I was still typing for the second input required in the chapter10 function.
Adding in the line of code: cin.ignore(numeric_limits<streamsize>::max(), '\n'); allowed me to cancel the input, and start a new one.
If you want to get all characters an end-user enters on a single line, use getline: instead of cin >> strinput write this:
getline(cin, strinput);
The fact that it is actually std::getline(std::cin, strinput) makes no difference, because your code uses std namespace anyway. In case you were wondering what std:: prefix is, it's a namespace of the Standard C++ library.
You can use getline() function
It copies into a string till a newline is reached or delimiter is found - so it will accept all the spaces till newline is reached
http://www.cplusplus.com/reference/string/string/getline/
or you can also use cin.getline() as shown here -
std::cin input with spaces?
use:
cin >> noskipws >> strinput;
Use std::getline() function. Example:
#include <iostream>
#include <vector>
#include <sstream>
void WordCounter(
const std::vector<std::string> & lines) {
for (int i = 0; i < lines.size(); ++i) {
std::istringstream iss(lines[i]);
std::string word;
int count = 0;
while (iss >> word) {
++count;
}
std::cout << "Line #" << i << " contains " << count << " words." <<
std::endl;
}
}
int main() {
std::string line;
std::vector<std::string> lines;
while (std::getline(std::cin, line)) {
lines.push_back(line);
}
WordCounter(lines);
return 0;
}