Why can't compare two strings in if condition? [closed] - c++

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Why can't compare two strings in if condition?
#include <iostream>
#include <string.h>
using namespace std;
int main() {
string sexo[20], feminino;
feminino = "f";
for (int i = 0; i < 3; i++) {
do {
cout << endl << "enter your " << i + 1 << "sexo: ";
cin >> sexo[i];
if (strcmp(sexo[i], feminino)==0){ // problem in here
cout << "that's ok" << endl;
}
} while (nome[i] == "0");
}
return 0;
}

You've been reading "tutorials" for C, or "tutorials" for C++ that actually teach you a terrible and outdated mix of C and C++.
The function strcmp is from the C Standard Library, and does not operate on the C++ std::string type.
To compare two std::strings, simply write:
if (sexo[i] == feminino) {
I find it hard to believe that your C++ book does not teach you this.

These are a few correct ways to compare these strings (in reverse order of preference)
if (strcmp(sexo[i].c_str(), feminino.c_str()) == 0) {
if (sexo[i].compare(feminino)) == 0) {
if (sexo[i] == feminino) {

You are using the wrong compare function. What you are using works with char * (it is used in C) but here you have std::string so you have to use std::string::compare()
Change your code to this:
#include <iostream>
#include <string.h>
using namespace std;
int main() {
string sexo[20], feminino; // problem in here
feminino = "f";
for (int i = 0; i < 3; i++) {
do {
cout << endl << "enter your " << i + 1 << "sexo: ";
cin >> sexo[i];
if (sexo[i].compare(feminito) == 0){
cout << "that's ok" << endl;
}
} while (nome[i] == "0");
}
return 0;
Note that you can also use sexo[i] == feminito as you have relational operators for std::string (see here for examples)

Related

Is it possible to put 2 option answer in string or char in c++? [closed]

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Is it okay or valid to use this? string answer = "A || B"; than using this if (answer == A || answer == B)?Because in my program I want to use that condition inside a while if statements. I want to put that two option condition in my while statement but it gets error.
// variables
string answerA = "Coin";
string guess;
int guessCount = 0;
int guessLimit = 3;
bool outOfGuesses = false;
cout << "Question A!\n" << endl;
cout << "A. What has a head and a tail, but no body?\n";
// if the answer is not correct, ask again only 3 times
while (answerA != guess && !outOfGuesses) {
if (guessCount < guessLimit) {
cout << "Answer: ";
cin >> guess;
guessCount++;
} else {
outOfGuesses = true;
}
}
if (outOfGuesses)
{
cout << "Your answers are all wrong! Better luck next time :)";
}
else
{
cout << "Your answer is Correct! ";
}
One std::string can hold only one string. You can use std::unordered_set to hold a set of multiple strings.
#include <iostream>
#include <string>
#include <unordered_set>
int main(void) {
std::unordered_set<std::string> accept_list = {"A", "B"};
std::string answer = "A";
if (accept_list.find(answer) != accept_list.end()) {
std::cout << "accept\n";
} else {
std::cout << "reject\n";
}
return 0;
}
(std::unordered_set is available since C++11. If your compiler doesn't support that, try std::set instead. Also initializer lists like accept_list = {"A", "B"} is since C++11, you may have to add each candidates separately in that case)

Convert lowercase to uppercase in a string [closed]

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The new typist in the printing cell is typing carelessly the jobs assigned. The typist while was supposed to type all the characters in upper case, has got in lower cases too. Your duty is to verify if all the characters are in upper case and do so if not. Also, notify how many mistakes the typist did.
Input bEGIN
Output BEGIN 1
I am getting wrong answer in some of the cases please help i am beginner
n=length of string
1<=n<=50
int main() {
string s;
cin >> s;
int ans = 0;
for (auto &c : s) {
if (islower(c)) {
ans++;
c = toupper(c);
}
}
cout << s;
cout << endl;
cout << ans;
return 0;
}
I think it includes spaces too, so instead of using >> operator use getline(cin,string), as >> gets terminate when whitespace is occurred.
#include <iostream>
using namespace std;
int main() {
string s;
getline(cin,s);
int ans = 0;
for (auto &c : s) {
if (islower(c)) {
ans++;
c = toupper(c);
}
}
cout << s;
cout << endl;
cout << ans;
return 0;
}
This might be a solution to other test cases.
This should work:
#include<stdio.h>
#include<iostream>
#include<string>
using namespace std;
int main() {
string s;
getline(cin,s);
int ans = 0;
for (auto &c : s) {
if (islower(c)) {
ans++;
c = toupper(c);
}
}
cout << s;
cout << endl;
cout << ans;
return 0;
}

error when calling char to allow user to enter choice [closed]

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I am writing a simple text game in C++. The user has the option of choosing the left room or the right room. I did have this set up as an int statement: enter 1 for left, enter 2 for right. Now I would like to have the user enter left for left room, right for right room.
I replaced the int with char, but I am getting an error.
#include <iostream>
using namespace std;
int main() {
char decision;
cin >> decision;
if (decision == left) {
cout << "went left" << endl;
}
return 0;
}
Error: comparison between pointer and integer
char stands for a single character - what you need is a string (multiple characters).
when you actually have the user's value in decision you need to compare it to the string "left" rather than just left which the compiler tries to interpret as a symbol (like a variable name).
All in all:
#include <iostream>
#include <string>
using namespace std;
int main() {
string decision;
cin >> decision;
if (decision == "left") {
cout << "went left" << endl;
}
return 0;
}
the easiest way use strcmp:
#include <iostream>
int main()
{
char decision[50] = "";
std::cout << "Decision: ";
std::cin.get(decision, 50, '\n');
if( !(strcmp(decision, "left")) )
std::cout << "left";
else
if( !(strcmp(decision, "right")) )
std::cout << "right";
else
std::cout << "bad input!" << std::endl;
std::cout << std::endl;
return 0;
}
you should also make no difference between lowercase and uppercase because if a user enters "Left" instead "left" then it won't work

I am getting C++ syntax error [closed]

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This script is supposed to read chars from keyboard, store them into arrays, and then output them:
#include <iostream>
#include <cstdlib>
#include <string>
using namespace std;
void storeArraysintoStruct(char[], int);
int main()
{
char test[] ="";
int a = 0;
storeArraysintoStruct(test, a);
system("pause");
return 0;
}
void storeArraysintoStruct(char test[], int a)
{
int n;
cout << "Enter number of entries: " << endl;
cin >> n;
int i = 0;
for (i=0, i<n, i++)
{
cout << "Enter your character: " << endl;
cin.getline(test, n);
}
while (i < n)
{
cout << test[i] << endl;
i++;
}
}
Edit: fixed it:
#include <iostream>
#include <cstdlib>
#include <string>
using namespace std;
void storeArraysintoStruct(char[], int);
int main()
{
char test[40] = "";
int a = 0;
storeArraysintoStruct(test, a);
system("pause");
return 0;
}
void storeArraysintoStruct(char test[], int a)
{
int n;
cout << "Enter number of entries: " << endl;
cin >> n;
int i;
for (i=0; i < n; i++)
{
cout << "Enter your character: " << endl;
cin >> test[i];
if (test[n-1])
{
cout << endl;
}
}
i =0;
while (i < n)
{
cout << test[i] << endl;
i++;
if(test[n-1])
{
cout << endl;
}
}
}
However, I am getting the errors Expected: primary expression before ")" and ";" before while. Any help will be greatly appreciated.
Edit: The script doesn't work as expected, for it doesn't output the stored characters. Any advice would be greatly appreciated.
The syntax error has already been pointed out in the comments. Also, as it has been mentioned, you never reset i after for loop, which prevents your while loop from running.
However, you have to also take in mind that this
char test[] = "";
allocates array test of only 1 character long. You cannot put more than one character of data into that array. In other words, your storeArraysintoStruct is sure to overrun the array and fall into undefined behavior territory.
In you want to preallocate a larger buffer for future use in storeArraysintoStruct, you have to specify the size explicitly. For example
char test[1000] = "";
will make test an array of 1000 characters. Of course, regardless of how large the array is, it is your responsibility to observe the size limit.
P.S. What is the point of that parameter a, if you never use it inside storeArraysintoStruct?

Reverse each character in a string except special characters (e.g. "?") [closed]

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For example : how are you? ----> woh era uoy?
This is my code, i got it worked but the question mark is besing reversed too.
How can i make it remained intact?
#include <iostream>
using namespace std;
int main()
{
string ch;
while(cin >> ch)
{
for(int i = ch.length() - 1; i >= 0; i--)
{
cout << ch[i];
}
cout << " ";
}
return 0;
}
Your chosen input method (cin >> ch) automatically splits the input into separate words.
Like Jerry Coffin said in his answer, you have to skip over punctuation etc to find to alpha characters to swap. Roughly like this:
#include <iostream>
#include <string>
#include <cctype>
using namespace std;
int main()
{
string ch;
while (cout << "String? " && cin >> ch)
{
cout << "Input: <<" << ch << ">>\n";
const char *bp = ch.c_str();
const char *ep = ch.c_str() + ch.length() - 1;
const char *sp = ch.c_str();
while (sp < ep)
{
while (sp < ep && (*sp != ' ' && !isalpha(*sp)))
sp++;
while (sp < ep && (*ep != ' ' && !isalpha(*ep)))
ep--;
char c = *sp;
ch[sp-bp] = *ep;
ch[ep-bp] = c;
sp++;
ep--;
}
cout << "Output: <<" << ch << ">>\n";
}
cout << endl;
return 0;
}
Sample dialogue
String? How are you?
Input: <<How>>
Output: <<woH>>
String? Input: <<are>>
Output: <<era>>
String? Input: <<you?>>
Output: <<uoy?>>
String? Pug!natious=punctuation.
Input: <<Pug!natious=punctuation.>>
Output: <<noi!tautcnu=psuoitanguP.>>
String?
You can tweak it from here. I'm far from claiming this is idiomatic C++; the use of const char * in the middle shows my C background.
Start from the beginning of the string, and scan forward until you find a letter. The scan backwards from the end until you find a letter. Swap them. Continue until the two positions meet.
Note: above I've used "letter", but all I really mean is "one of the characters that should be reversed." You haven't defined very precisely which characters should be swapped and which shouldn't, but I'm assuming you (or your teacher) has a reasonably specific definition in mind.
Try using array and scanning each letter to see if there is a question mark. If there is, move it to the last place of the array.
simple solution or hack to solve this case alone. if there are more cases comment it lets solve it together.
#include <iostream>
using namespace std;
int main()
{
string ch;
while(cin >> ch)
{
int flag = 0;
for(int i = ch.length() - 1; i >= 0; i--)
{
if(ch[i] != '?')
cout << ch[i];
else
flag = 1;
}
if(flag)
cout << "?";
else
cout << " ";
}
return 0;
}