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I have to write a function that goes through a string, finds any capital letters present and makes them lowercase. I decided to add a bit of code to show what letters were found and how many were found. Although on each compilation, the value of 'cnt' yields ridiculous results.
#include <iostream>
#include <vector>
using namespace std;
int upper(string s) {
int cnt;
vector<char> v{};
for (auto& i : s) {
if (isupper(i)) {
v.push_back(i);
i = tolower(i);
++cnt;
}
}
cout << "new string is '" << s << "'\n"
<< "number of capitals found is " << cnt << "\n"
<< "letters found were ";
for (auto l : v)
cout << l << " ";
return 0;
}
int main() {
string l = "This IS a TeSt";
upper(l);
}
I'm sure I must have done something wrong with the loop but whatever the problem is, I cannot find it.
The variable cnt is never initialized when used, change
int cnt;
to
int cnt = 0;
You failed to initialize the local variable cnt. Using an uninitialized value provokes undefined behavior, under which basically anything can happen.
Use int cnt=0; and please turn on all your compiler warnings.
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I just started learning C++. I have seen examples of coders typing code like this...
int main() {
cout << "hello";
<< "world";
return 0;
}
but when I tried that it seemed to me that I have to write it like this...
int main() {
cout << "hello";
cout << "world";
return 0;
}
How can I do this like the original example shows?
You might mean:
int main() {
cout << "hello" // <- no trailing `;`
<< "world";
return 0;
}
That will print:
helloworld
If you wanted then on separated rows, you can write:
int main() {
cout << "hello\n"
<< "world\n";
return 0;
}
That will produce:
hello
world
But, there is another, less known, feature of the compiler - concatenation
of raw strings:
int main() {
cout << "hello"
"world";
return 0;
}
That will also work. This too gives helloworld as output.
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I have simplified the code to get rid of unrelated objects. This is my code:
#include <iostream>
#include <fstream>
using namespace std;
fstream asdf;
int input;
void import_image(){
asdf.seekg(0);
char character;
for(int k = 0; k < 40; k++){
asdf.get(character);
input = (unsigned int)(unsigned char)character;
}
}
void print_hello_world(){
for(int rows; rows <= 27; rows++){
cout << "hello world" << endl;
}
cout << "goodbye.";
}
int main(){
asdf.open("abc.txt", ios::binary | ios::in);
cout << asdf.is_open() << endl;
import_image();
//cout << endl;
print_hello_world();
return 0;
}
Running this code results only in
1
goodbye.
--------------------------------
Process exited after 0.1511 seconds with return value 0
however removing double slash (simply adding cout << endl;) fixes everything. I have no idea why it happens and would like to now why is it so. I know that variable "rows" has no value, but why does printing a new line fix everything?
The new "endl"
is a great sign
that what you see,
is called "UB".
Your program has Undefined Behavior (UB) because your int rows that you use for the loop iterations is uninitialized.
By UB definition anything may happen. Activate all (sane) compiler warnings to find errors like this earlier in your development process.
Undefined behavior yield working programs by completely random changes (for example the addition of std::endl) but in the end it's undefined behavior.
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I'm a student who just learned to use C++ for a few weeks. I write C++ code on Code:: Block and I am trying to run this code to learn about vector:
#include <iostream>
#include <vector>
#include <string>
using namespace std;
int main()
{
vector<int> intVector;
for(int i = 0; i < 10; i++)
{
intVector.push_back(i+1);
}
cout << "Numbers in vector: ";
for(int i = 0; i < intVector.size(); i++)
{
cout << intVector[i] + " ";
}
}
But the output is really weird:
Numbers in vector: vector::_M_emplace_back_auxector::_M_emplace_back_auxctor::_M_emplace_back_auxtor::_M_emplace_back_auxor::_M_emplace_back_auxr::_M_emplace_back_aux::_M_emplace_back_aux:_M_emplace_back_aux_M_emplace_back_aux
Process returned 0 (0x0) execution time : 0.047 s
Press any key to continue.
Does anyone know how to fix this problem? Do I use vector in the wrong way?
Try changing the cout line like this:
cout << intVector[i] << " ";
What you're trying to do is add an int& and a string literal -- in some compilers it will emit a warning indicating for you that you're not getting what you intended for.
For example with Clang:
warning: adding '__gnu_cxx::__alloc_traits>::value_type' (aka 'int') to a string does not append to the string [-Wstring-plus-int]
cout << intVector[i] + " ";
~~~~~~~~~~~~~^~~~~
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i was extracting lowercase and uppercase characters from a string . then print those uppercase and lowercase string in sorted order in .to sort the string i used std::sort function .but it's not working.
here is my code
#include <bits/stdc++.h>
using namespace std;
int main() {
//std::ios::sync_with_stdio(false);
char str[1005];
char low[1005];
char upr[1005];
int n;
int t;
cin>>t;
while(t--)
{
cin>>n;
cin>>str;
low[0]='\0';
upr[0]='\0';
int i=0,j=0,k=0;
while(i<n)
{
(str[i]>='A' && str[i]<='Z') ? (upr[j]=str[i],++j) : (low[k]=str[i],++k) ;
++i;
}
low[j]='\0';
upr[k]='\0';
cout<<"lowercase="<<low<<'\n';
cout<<"uppercase="<<upr<<'\n';
sort(low,low+j);
sort(upr,upr+k);
cout<<"lowercase="<<low<<'\n';
cout<<"uppercase="<<upr<<'\n';
}
return 0;
}
test case:
1 // number of test cases
15 // length of string
abHJUdjKIpwlaKm
output:
lowercase=abdjpw //before sorting
uppercase=HJUKIK //before sorting
lowercase=abdjpw //after sorting
uppercase= //after sorting
after sorting uppercase string don't even print.
You have a bug with indexes, fix:
low[k] = '\0';
upr[j] = '\0';
cout << "lowercase=" << low << '\n';
cout << "uppercase=" << upr << '\n';
sort(low, low + k);
sort(upr, upr + j);
cout << "lowercase=" << low << '\n';
cout << "uppercase=" << upr << '\n';
Exchanged k and j in this snippet.
Better variable names would help. Try replacing j and k with something more descriptive like lowIndex and uprIndex. Then you should see the problem.
I noticed you were using j variable for uppercase and k for lowercase in the while loop then proceeded to do the opposite later. Was this intentional? Wondering if that's causing a bug.
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Whenever I try to run this program it returns an error saying:
no operator "<<" matches these operands
Also note that the program only runs into this problem in the getChoice() function.
#include <iostream>
#include "utilities.h"
using namespace std;
int getChoice(string inChoices[]){
int numOfChoices = sizeof(inChoices) / sizeof(inChoices[0]);
string x = inChoices[0];
string y = inChoices[1];
cout << x << endl << y << endl;
return numOfChoices;
}
int main()
{
string choices[2] = { "Happy Day", "Even Better Day" };
cout << utilities::getChoice(choices) << endl;
cout << endl << sizeof(choices) / sizeof(choices[0]) << endl;
}
You need also to include the string header:
#include <string>
You need to #include <string>
And your calculation of numOfChoices in getChoice() is wrong, since the parameter inChoices is actually a "pointer to string" instead of "array of strings".