Vector subscript out of range - vector of structures - c++

I have the following code. It's supposed to count the number of repetitions of the given letter in a given file. However, when i try to run this i get the Vector subscript out of range. Other people with the same error were trying to access undefined parts of it, but this doesn't seem to be an issue here i think.
struct letters
{
char letter;
int repetitions=0;
};
void howManyTimes(const string &output)
{
ifstream file(output);
vector <letters> alphabet;
for (int i = 0; i < 'z' - 'a' + 1; i++)
{
alphabet[i].letter = 'a' + i;
}
string line;
while (file.eof() == 0)
{
getline(file, line);
for (char c : line)
{
if(c >= 'a' && c <= 'z')
alphabet[c - 'a'].repetitions++;
else if (c >= 'A' && c >= 'Z')
alphabet[c - 'A'].repetitions++;
}
}
cout << alphabet[10].repetitions;
}

vector <letters> alphabet; // (1)
for (int i = 0; i < 'z' - 'a' + 1; i++)
{
alphabet[i].letter = 'a' + i; // (2)
}
(1) creates an empty vector.
Inside the for loop in (2) you try to access items using the index i in an empty vector, so clearly your index is out of range.
You first have to populate the vector with some data, then you can access this data.
If you want to add new items to the vector, you can use vector::push_back (which is probably what you meant in (2)).

I don't see the part of your code where alphabet is expanded to accommodate the objects you plan to store in it. std::vector only resizes itself when you use the push_back, insert, emplace or other similar methods; it doesn't do so when accessing directly using the operator[] method.
At any rate, for a task like this, I'm not sure you'd want to use a vector, when a std::map<char, int64_t> would probably be a lot cleaner, and would let you preserve the syntax you're trying to use without tons of extra maintenance.
void howManyTimes(const string &output)
{
ifstream file(output);
map<char, int64_t> alphabet;
string line;
while (getline(file, line))
{
for (char c : line)
{
if(c >= 'a' && c <= 'z')
alphabet[c - 'a']++;
else if (c >= 'A' && c >= 'Z')
alphabet[c - 'A']++;
}
}
cout << alphabet[10];
}

Other people with the same error were trying to access undefined parts of it, but this doesn't seem to be an issue here I think.
It is definitely an issue here:
vector <letters> alphabet; // Now size of the vector is 0.
for (int i = 0; i < 'z' - 'a' + 1; i++)
{
// You are trying to access elements 0, 1, 2, ..., which do not exist.
alphabet[i].letter = 'a' + i;
}
The simplest solution is to construct your vector with appropriate size:
vector <letters> alphabet('z' - 'a' + 1);

This program is really powerful for what the question is asking (makes me wonder how my students felt when I gave it as a homework assignment :) ). Do you have to use a struct? Let's assume not, and also assume we know the size of the alphabet, and that 'a' is the first letter and 'z' is the last letter:
vector<int> repetitions(26, 0);
char nextCharacter;
while( !file.eof() )
{
cin >> nextCharacter;
nextCharacter = tolower(nextCharacter);
if(nextCharacter >= 'a' && nextCharacter <= 'z')
{
repetitions[nextCharacter - 'a']++;
}
}
To check for a letter:
cin >> letterToQuery;
cout <<"The amount of occurrences of " << letterToQuery <<" is ";
cout << repetitions[tolower(letterToQuery) - 'a'] << endl;
If you don't know the size of your alphabet, the code changes to:
vector<int> repetitions('last_alphabet' - 'a' + 1, 0);
...
if(nextCharacter >= 'a' && nextCharacter <= 'last_letter')
And finally, if you DO have to use that struct, your code changes to:
struct Letter
{
char letter;
int repetitions=0;
};
vector<Letter> alphabet;
letter temp;
for(int i = 0; i < 'last_alphabet' - 'a' + 1; ++i)
{
temp.letter = 'a' + i;
alphabet.push_back(temp);
}
// then everything else is a similar structure
char nextCharacter;
while( !file.eof() )
{
cin >> nextCharacter;
nextCharacter = tolower(nextCharacter);
if(nextCharacter >= 'a' && nextCharacter <= 'last_alphabet')
{
alphabet[nextCharacter - 'a'].repetitions++;
}
}
To check for a letter:
cin >> letterToQuery;
cout <<"The amount of occurrences of " << letterToQuery <<" is ";
cout << alphabet[tolower(letterToQuery) - 'a'].repetitions << endl;
Notice, if you replace 'last_alphabet' with 'z', you get the current alphabet.

Related

What is wrong with my program to find the longest word in a sentence?

#include <iostream>
using namespace std;
int main() {
char a[101]{0};
cin>>a;
cin.getline(a,101);
cin.ignore();
int currLen{0};
int maxLen{0};
int startInd{-1};
int endInd{-1};
for(int i=0; i<101; i++) {
if(a[i]!=' ' ) {
++currLen;
} else if(a[i]==' '||a[i]=='\0') {
if(currLen>maxLen) {
maxLen=currLen;
startInd=i-currLen;
endInd=i-1;
}
if(a[i]=='\0')
break;
currLen=0;
}
}
cout<<maxLen<<endl;
if(startInd==-1)
cout<<-1;
else
for(int i=startInd; i<=endInd; i++)
cout<<a[i];
return 0;
}
If I take an input here, for example, "My name is Manav Kampani"
It will output 5
Manav instead of 7
Kampani
But if I write "My name is Manav Kampani ", with space after the last word
than it is considering Kampani too printing Kampani.
Also when I input "Kampani Manav is my name" then too it's displaying the wrong output. That means it is not considering the first word of the sentence.
if(a[i]!=' ' )
{
++currLen;
}
else if(a[i]==' '||a[i]=='\0')
{
....
}
Consider the case of a[i] == 0. Which of these if-statements will apply.
Answer: the first one. Which means you'll never look at the final word in the string. You also don't exit at the end of the string, but instead loop through whatever is in your string all the way out to character 101.
As a general structure, be very, very careful with this:
if (condition)
else if (condition)
// without a final else section
If you do that, you need to think about what you're doing. In this particular case, you can have:
if (a[i] != 0 && a[i] != ' ')
else
It may not solve all your issues, but it should solve some.
A nice sliding window pattern implementation.
You have 3 problems in your code
You must not write cin >> a;
You must not write cin.ignore();
You need to modify your if statement like so: if (a[i] != ' ' && a[i] != '\0') Otherwise you will not detect the last word.
Your complete working code with that minor fixes will lokk like that.
int main()
{
char a[101]{ 0 };
//cin >> a;
cin.getline(a, 101);
//cin.ignore();
int currLen{ 0 };
int maxLen{ 0 };
int startInd{ -1 };
int endInd{ -1 };
for (int i = 0; i < 101; i++)
{
if (a[i] != ' ' && a[i] != '\0')// Add comparison
{
++currLen;
}
else if (a[i] == ' ' || a[i] == '\0')
{
if (currLen > maxLen)
{
maxLen = currLen;
startInd = i - currLen;
endInd = i - 1;
}
if (a[i] == '\0')
break;
currLen = 0;
}
}
cout << maxLen << endl;
if (startInd == -1)
cout << -1;
else
for (int i = startInd; i <= endInd; i++)
cout << a[i];
return 0;
}
Additionally. You should not use C-Style arrays in C++. And please use std::string
There is a couple of things here:
1- You don't need to do a cin>>a this is actually consuming the first word, and afterwards the content is overrided by cin.getline(). So removing the firsst cin>>ayou'll be fine.
2- The last word is not read because there isn't any if condition that matches the condition aka.
if(a[i]!=' ' ) case of not a space
//not end of word
else if(a[i]==' '||a[i]=='\0') case of space or null
//end of word
So your last character is not a space nor null, that means you don't detect the last word.

C++ - Changing single lowercase charachter in a word to uppercase and vice versa using struct data type

As you can see from the title I want to change lowercase charachter in word to uppercase and vice versa.
Also I need to use struct object (in my case name).
I have a problem when I change charachter from lowercase to uppercase it only changes in the first word not in the second,third and so on. I am also reading words from file
Here is the input file
Aayak Audi
Ahmed Golf7
Samed Golf5
Here is the code
#include <iostream>
#include <fstream>
#include <string>
#include <algorithm>
#include <cctype>
using namespace std;
struct pismaStr
{
string ime;
string objekat;
};
void malaVelikaSlova (string name)
{
for (int i = 0; i < name.length()-1; i++)
{
if (name.at(i) >= 'A' && name.at(i) <= 'Z')
name.at(i) += 32;
else if (name.at(i) >= 'a' && name.at(i) <= 'z')
name.at(i) -= 32;
cout << name;
break;
}
}
int main()
{
ifstream pismo;
pismo.open("pismo.txt");
ofstream novoPismo;
novoPismo.open("novaSlova.txt");
pismaStr stvari[200];
int brojStvari = 0;
while(pismo >> stvari[brojStvari].ime >> stvari[brojStvari].objekat)
{
brojStvari++;
}
for (int i = 0; i < brojStvari; i++)
{
vector <pismaStr> vec = {pismaStr{stvari[i].ime}};
for (auto obj : vec)
{
malaVelikaSlova (obj.ime);
}
}
Here is the output:
aayak
ahmed
samed
It was:
Aayak
ahmed
samed
I want it to look like this
aAYAK
sAMED
aHMED
How can I fix this?
Any tips?
Tangential,
but it will be an issue, is this line
for (int i = 0; i < name.length()-1; i++)
This will loop from name[0] to name[name.length() - 2]. The std::string::length returns the number of usable characters. It does not include the null terminator, so you don't need to subtract 1. It should be
for (int i = 0; i < name.length(); i++)
Your bigger problem
is the break statement at the end of your loop (indentation added for clarity)
for (int i = 0; i < name.length()-1; i++)
{
if (name.at(i) >= 'A' && name.at(i) <= 'Z')
name.at(i) += 32;
else if (name.at(i) >= 'a' && name.at(i) <= 'z')
name.at(i) -= 32;
cout << name;
break; // <--- this exits the loop entirely
}
Your break; tells the program to exit the loop immediately. No further iterations of the loop are performed. Your cout statement is also within the loop. Once you do get the loop running for each iteration, you'll output each step of the transformation. To only output it once (at the end) you put it outside of the loop. If you want to loop over every character (and you do), your final code looks like
void malaVelikaSlova (string name)
{
for (int i = 0; i < name.length() - 1; i++)
{
if (name.at(i) >= 'A' && name.at(i) <= 'Z')
name.at(i) += 32;
else if (name.at(i) >= 'a' && name.at(i) <= 'z')
name.at(i) -= 32;
}
cout << name;
}
Other things you can change
You don't need to do bounds checking on your string indexes, since you're looping based on the string length, and it's not changing, so you don't need to extra overhead of std::string::at. You can just use the index operator:
// name.at(i); // <-- no need to do this anywhere
name[i] // <-- slightly faster
Since you're applying some operation to each element (character) in your container (string), this is a great candidate for std::transform, from the <algorithm> library. I'm also using a lambda expression here, which is a great too from C++ to get familiar with.
https://en.cppreference.com/w/cpp/algorithm/transform
https://en.cppreference.com/w/cpp/language/lambda
void malaVelikaSlova (string name)
{
std::transform(
name.begin(),
name.end(),
[](char c) -> char
{
if (c >= 'A' && c <= 'Z')
return c + 32;
if (c >= 'a' && c <= 'z')
return c - 32;
return c; // <-- for all other characters
}
);
std::cout << name << "\n";
}
You could even take advantage of the std::isupper, std::islower, std::toupper, and std::tolower functions to make your code more explicit. Note that std::string is an alias for std::basic_string<char> (its value type is char), the upper and lower functions operate on unsigned chars, so you'll need to convert the chars to unsigned chars:
https://en.cppreference.com/w/cpp/string/basic_string
https://en.cppreference.com/w/cpp/string/byte/tolower
https://en.cppreference.com/w/cpp/string/byte/toupper
https://en.cppreference.com/w/cpp/string/byte/isupper
https://en.cppreference.com/w/cpp/string/byte/islower
void malaVelikaSlova (string name)
{
std::transform(
name.begin(),
name.end(),
[](unsigned char c) -> unsigned char // <-- must convert to unsigned to be safe with upper/lower functions
{
if std::isupper(c) return std::tolower(c);
if std::islower(c) return std::toupper(c);
return c; // <-- for all other characters
}
);
std::cout << name << "\n";
}

Prevent loop from echoing if another same-value array element has been already echoed in C++

First of all, sorry for the mis-worded title. I couldn't imagine a better way to put it.
The problem I'm facing is as follows: In a part of my program, the program counts occurences of different a-zA-Z letters and then tells how many of each letters can be found in an array. The problem, however, is this:
If I have an array that consists of A;A;F;A;D or anything similar, the output will be this:
A - 3
A - 3
F - 1
A - 3
D - 1
But I am required to make it like this:
A - 3
F - 1
D - 1
I could solve the problem easily, however I can't use an additional array to check what values have been already echoed. I know why it happens, but I don't know a way to solve it without using an additional array.
This is the code snippet (the array simply consists of characters, not worthy of adding it to the snippet):
n is the size of array the user is asked to choose at the start of the program (not included in the snippet).
initburts is the current array member ID that is being compared against all other values.
burts is the counter that is being reset after the loop is done checking a letter and moves onto the next one.
do {
for (i = 0; i < n; i++) {
if (array[initburts] == array[i]) {
burts++;
}
}
cout << "\n\n" << array[initburts] << " - " << burts;
initburts++;
burts = 0;
if (initburts == n) {
isDone = true;
}
}
while (isDone == false);
Do your counting first, then loop over your counts printing the results.
std::map<decltype(array[0]), std::size_t> counts;
std::for_each(std::begin(array), std::end(array), [&counts](auto& item){ ++counts[item]; });
std::for_each(std::begin(counts), std::end(counts), [](auto& pair) { std::cout << "\n\n" << pair.first << " - " pair.second; });
for (i = 0; i < n; i++)
{
// first check if we printed this character already;
// this is the case if the same character occurred
// before the current one:
bool isNew = true;
for (j = 0; j < i; j++)
{
// you find out yourself, do you?
// do not forget to break the loop
// in case of having detected an equal value!
}
if(isNew)
{
// well, now we can count...
unsigned int count = 1;
for(int j = i + 1; j < n; ++j)
count += array[j] == array[i];
// appropriate output...
}
}
That would do the trick and retains the array as is, however is an O(n²) algorithm. More efficient (O(n*log(n))) is sorting the array in advance, then you can just iterate over the array once. Of course, original array sequence gets lost then:
std::sort(array, array + arrayLength);
auto start = array;
for(auto current = array + 1; current != array + arrayLength; ++current)
{
if(*current != *start)
{
auto char = *start;
auto count = current - start;
// output char and count appropriately
}
}
// now we yet lack the final character:
auto char = *start;
auto count = array + arrayLength - start;
// output char and count appropriately
Pointer arithmetic... Quite likely that your teacher gets suspicious if you just copy this code, but it should give you the necessary hints to make up your own variant (use indices instead of pointers...).
I would do it this way.
#include <iostream>
#include <string>
#include <vector>
using namespace std;
int main()
{
string s;
vector<int> capCount(26, 0), smallCount(26, 0);
cout << "Enter the string\n";
cin >> s;
for(int i = 0; i < s.length(); ++i)
{
char c = s.at(i);
if(c >= 'A' && c <= 'Z')
++capCount[(int)c - 65];
if(c >= 'a' && c <= 'z')
++smallCount[(int)c - 97];
}
for(int i = 0; i < 26; ++i)
{
if(capCount[i] > 0)
cout << (char) (i + 65) << ": " << capCount[i] << endl;
if(smallCount[i] > 0)
cout << (char) (i + 97) << ": " << smallCount[i] << endl;
}
}
Note: I have differentiated lower and upper case characters.
Here's is the sample output:
output

C++ - Last value in array gets duplicated in map

I'm trying to create a dictionary of words from a sentence using a map and an array of strings. My problem is every time I loop through to add values to the map from my array the last item always gets duplicated as a key. This is all on xCode by the way.
int main(){
char input[50];
int i = 0,
arr_size = 0;
string s[20];
cout << "Please input a phrase: ";
cin.getline(input, 50);
while(i < sizeof(input) - 1)
{
input[i] = tolower(input[i]);
if(isspace(input[i]) || ispunct(input[i]) )
arr_size++;
else
s[arr_size].operator+=(input[i]);
i++;
}
map<string, int> dictionary;
for (i = 0; i < arr_size; i++) {
if(dictionary.map::find(s[i]) == dictionary.end())
dictionary.insert(make_pair(s[i], 1));
else
dictionary.at(s[i])++;
}
typedef map<string, int>::const_iterator MapIt;
for (MapIt iter = dictionary.begin(); iter != dictionary.end(); iter++)
{
cout << iter->first << " : " << iter->second << endl ;
}
}
With my output looking something like this:
Please input a phrase: thE Blue Black BluE Cat Cat BLacK hat zap zap
black : 2
blue : 2
cat : 2
hat : 1
the : 1
zap : 1
zap : 1
The two "zap"'s are not the same. Probably the last one contains a newline character, '\n'. More generally, you need to learn how to index loops properly.
So it turns out while I was looping through
while(i < sizeof(input) - 1)
{
input[i] = tolower(input[i]);
if(isspace(input[i]) || ispunct(input[i]) )
arr_size++;
else
s[arr_size].operator+=(input[i]);
i++;
}
I didn't check for any other characters besides punctuation and space so it was reading in everything else.
for(int i = 0; i < sizeof(input) - 1; i++)
{
if(isspace(input[i]) || ispunct(input[i]))
arr_size++;
else if (isalpha(input[i])){
input[i] = tolower(input[i]);
s[arr_size].operator+=(input[i]);
}
}
This code worked out better and is indexed a little better.

my code doesn't run some thing wrong about strings, c++

I was training on solving algorithms, I wrote a code but it won't compile
in (if) I can not check s[i]=='S' .
I'm trying to if s[i] is S character or not but I don't know where my problem is.
If I can't use this syntax, what could be a solution?
#include<iostream>
#include<string>
using namespace std;
int main()
{
double v_w=25,v_s=25,d_w=25,d_s=25;
int n;
cin>>n;
string s[]={"WSSS"};
int i ;
for (i=0; i<n; i++)
{
if( s[i] == "W" )
{
v_s += 50;
d_w = d_w + (v_w/2);
d_s = d_s + (v_s/2);
cout<<"1 \n";
}
if(s[i]=='W')
{
v_w +=50;
d_w = d_w + (v_w/2);
d_s = d_s + (v_s/2);
cout<<"2 \n";
}
return 0;
}
cout<< d_w<<endl<<d_s;
}
string s[]={"WSSS"}; means an array of strings which the first one is "WSSS".
What you need is:
std::string s="WSSS";
string s[] = {"Hello"} is an array of strings (well, of one string).
If you iterate over it, or index into it s[0] is "Hello".
Whereas
string s{"Hello"} is one string, which is made up of characters.
If you iterate over it, or index into it s[0], you will get 'H'.
To pre-empt all the other things that are going to go wrong when the string versus character problem is sorted, lets move the return 0; from the middle of the for loop.
Then let's think about what happens if the number n entered is larger than the length of the string:
int n;
cin>>n; //<- no reason to assume this will be s.length (0 or less) or even positive
string s{"WSSS"}; //one string is probably enough
int i ;
for(i=0;i<n;i++)
{
if( s[i] == 'W' ) //ARGGGGGGG may have gone beyond the end of s
{
In fact, let's just drop that for now and come back to it later. And let's use a range based for loop...
#include<iostream>
#include<string>
using namespace std;
int main()
{
double v_w = 25, v_s = 25, d_w = 25, d_s = 25;
string s{ "WSSS" };
for (auto && c : s)
{
if (c == 'W')
{
v_w += 50;
d_w = d_w + (v_w / 2);
d_s = d_s + (v_s / 2);
cout << "2 \n";
}
}
cout << d_w << '\n' << d_s << '\n'; //<- removed endl just because...
return 0;
}
s is an array of strings in this case it has only element:
string s[] = {"WSSS"};
so writing s[2]; // is Undefined behavior
your code will produce a UB if the user enters n greater than the number of elements in s:
n = 4;
for(i = 0; i < n; i++) // s[3] will be used which causes UB
{
if( s[i] == 'W' ) // s[i] is a string not just a single char
{
}
}
also as long as s is an array of strings then to check its elements check them as strings not just single chars:
if( s[i] == "W" ) // not if( s[i] == 'W' )
I think you wanted a single string:
string s = {"WSSS"};
because maybe you are accustomed to add the subscript operator to character strings:
char s[] = {"WSSS"};
if so then the condition above is correct:
if( s[i] == 'W' )