The code is to read instructions from text file and print out graphic patterns. One is my function is not working properly. The function is to read the vectors of strings I've got from the file into structs.
Below is my output, and my second, third, and sixth graphs are wrong. It seems like the 2nd and 3rd vectors are not putting the correct row and column numbers; and the last one skipped "e" in the alphabetical order.
I tried to debug many times and still can't find the problem.
typedef struct Pattern{
int rowNum;
int colNum;
char token;
bool isTriangular;
bool isOuter;
}Pattern;
void CommandProcessing(vector<string>& , Pattern& );
int main()
{
for (int i = 0; i < command.size(); i++)
{
Pattern characters;
CommandProcessing(command[i], characters);
}
system("pause");
return 0;
}
void CommandProcessing(vector<string>& c1, Pattern& a1)
{
reverse(c1.begin(), c1.end());
string str=" ";
for (int j = 0; j < c1.size(); j++)
{
bool foundAlpha = find(c1.begin(), c1.end(), "alphabetical") != c1.end();
bool foundAll = find(c1.begin(), c1.end(), "all") != c1.end();
a1.isTriangular = find(c1.begin(), c1.end(), "triangular") != c1.end() ? true : false;
a1.isOuter = find(c1.begin(), c1.end(), "outer") != c1.end() ? true : false;
if (foundAlpha ==false && foundAll == false){
a1.token = '*';
}
//if (c1[0] == "go"){
else if (c1[j] == "rows"){
str = c1[++j];
a1.rowNum = atoi(str.c_str());
j--;
}
else if (c1[j] == "columns"){
str = c1[++j];
a1.colNum = atoi(str.c_str());
j--;
}
else if (c1[j] == "alphabetical")
a1.token = 0;
else if (c1[j] == "all"){
str = c1[--j];
a1.token = *str.c_str();
j++;
}
}
}
Before debugging (or posting) your code, you should try to make it cleaner. It contains many strange / unnecessary parts, making your code harder to understand (and resulting in the buggy behaviour you just described).
For example, you have an if in the beginning:
if (foundAlpha ==false && foundAll == false){
If there is no alpha and all command, this will be always true, for the entire length of your loop, and the other commands are all placed in else if statements. They won't be executed.
Because of this, in your second and third example, no commands will be read, except the isTriangular and isOuter flags.
Instead of a mixed structure like this, consider the following changes:
add a default constructor to your Pattern struct, initializing its members. For example if you initialize token to *, you can remove that if, and even the two bool variables required for it.
Do the parsing in one way, consistently - the easiest would be moving your triangular and outer bool to the same if structure as the others. (or if you really want to keep this find lookup, move them before the for loop - you only have to set them once!)
Do not modify your loop variable ever, it's an error magnet! Okay, there are some rare exceptions for this rule, but this is not one of them.
Instead of str = c1[++j];, and decrementing later, you could just write str = c1[j+1]
Also, are you sure you need that reverse? That makes your relative +/-1 indexing unclear. For example, the c1[j+1 is j-1 in the original command string.
About the last one: that's probably a bug in your outer printing code, which you didn't post.
Related
In this program, the user must type in an 3 letter departing airport code (userFlight) and I will give them back the possible destinations. To check that what they typed in is one of the valid airport codes (departureAirport) I want to compare userFlight and make sure it is one of the possible departureAirports which I have stored in a vector called flights[]. This code obviously isn't working, but is there a similar way to accomplish this?
if
(for (j = 0, j < flights.size, j++)
{
(userFlight != flights[j].departAirport)
})
{return errorCode};
else
{//doSomething()};
If it has a operator< inside which does compare like your condition, how about
if(std::find(flights.begin(), flights.end(), userFlight) != flights.end())
{
/* found */
}
else
{
/* not found */
}
Else, if you don't like that, just check if the loop runs through all indices:
size_t i;
for (i = 0, i < flights.size, i++)
{
if(userFlight == flights[i].departAirport)
break;
}
if(i < flights.size)
{
/* found */
}
else
{
/* not found */
}
But no, a syntax like you want doesn't exist.
The code structure you were aiming for is:
for (j = 0; j < flights.size(); j++)
if (userFlight == flights[j].departAirport)
break;
if ( j == flights.size() ) // we got to the end
return errorCode;
doSomething(j);
However, this is a C-like code style. Not that there is anything wrong with that, but C++ allows for algorithms to be expressed more abstractly (and therefore, easier to read and maintain). IMHO it would be better to use one of the other suggestions such as std::set or std::find_if.
It sounds like you actually want to have a std::set of departing airports.
std::set<std::string> departing_airports = {"DTW", "MKE", "MSP", };
assert(departing_airports.count("DTW") == 1);
Yet another option is std::any_of. Assuming flights contains objects of type Flight:
if (std::any_of(std::begin(flights), std::end(flights),
[&](const Flight& f) { return userFlight == f.departAirport; }))
return errorCode;
doSomething();
I'm trying to work on a string comparison check for an introductory C++ course; it's an online course and unfortunately the instructor is not very responsive. For a current lab, I need to perform a number of manipulations on string data.
Currently, I'm working on a step to check if a string has any repeated characters, and if a repetition is found, to delete the repeated characters at their present spot and move one copy of the letter to the beginning of the string. This is only to be done for the first double to be found.
I've set up a basic counter to move through the string looking for matches, checking a stored character (updated on each iteration) to the current position in the string.
I tried multiple string functions (comparing the current inputString[i] to the previous such, stored as a second string tempStore), but those always gave char conversion errors. I've tried the below instead, but this is now giving an error: "invalid conversion from 'char' to 'const char*'.
inputString is given by the user, testA and testB are defined as type char
Any ideas?
while (opComplete == false) {
if (i == 0) {
i++;
}
else if (i == inputString.size()) {
//Not Found
opComplete = true;
}
else if (i > 0) {
testA = inputString[i-1];
testB = inputString[i];
if (strcmp(testA,testB) != 0) {
i++;
}
else {
inputString.insert(0,inputString[i]);
inputString.erase(i,1);
inputString.erase(i-1,1);
opComplete = true;
}
}
}
Your problem is in this line:
inputString.insert(0,inputString[i]);
The std::string.insert() function the way you call it here has the following signature:
string& insert ( size_t pos1, const char* s );
so it expects a const char pointer. You, however, are giving it the inputString[i]. The return value of std::string.operator[] is a reference (as here), hence the error. However, by the time you reach your else, you already have the desired character in your testB variable, so you can just change the line to
inputString.insert(0, &testB);
You also can't pass normal chars into strcmp. You can use operator==, or, in your case, operator!= though.
You are using the insert method incorrectly, check its reference here for possible arguments.
while (opComplete == false)
{
if (i == 0)
i++;
else if (i == inputString.size())
opComplete = true;
else if (i > 0) {
char testA = inputString[i-1];
char testB = inputString[i];
if(testA!=testB)
i++;
else {
inputString.insert(0,&testB); //Problem Corrected here.
inputString.erase(i,1);
inputString.erase(i-1,1);
opComplete = true;
}
}
}
I'm iterating through an array of chars to do some manipulation. I want to "skip" an iteration if there are two adjacent characters that are the same.
e.g. x112abbca
skip----------^
I have some code but it's not elegant and was wondering if anyone can think of a better way? I have a few case's in the switch statement and would be happy if I didn't have to use an if statement inside the switch.
switch(ent->d_name[i])
{
if(i > 0 && ent->d_name[i] == ent->d_name[i-1])
continue;
case ' ' :
...//code omited
case '-' :
...
}
By the way, an instructor once told me "avoid continues unless much code is required to replace them". Does anyone second that? (Actually he said the same about breaks)
Put the if outside the switch.
While I don't have anything against using continue and break, you can certainly bypass them this time without much code at all: simply revert the condition and put the whole switch statement within the if-block.
Answering the rectified question: what's clean depends on many factors. How long is this list of characters to consider: should you iterate over them yourself, or perhaps use a utility function from <algorithm>? In any case, if you are referring to the same character multiple times, perhaps you ought to give it an alias:
std::string interesting_chars("-_;,.abc");
// ...
for (i...) {
char cur = abc->def[i];
if (cur != prev || interesting_chars.find(cur) == std::string::npos)
switch (current) // ...
char chr = '\0';
char *cur = &ent->d_name[0];
while (*cur != '\0') {
if (chr != *cur) {
switch(...) {
}
}
chr = *cur++;
}
If you can clobber the content of the array you are analyzing, you can preprocess it with std::unique():
ent->erase(std::unique(ent->d_name.begin(), ent->d_name.end()), ent.end());
This should replace all sequences of identical characters by a single copy and shorten the string appropriately. If you can't clobber the string itself, you can create a copy with character sequences of just one string:
std::string tmp;
std::unique_copy(ent->d_name.begin(), ent->d_name.end(), std::back_inserter(tmp));
In case you are using C-strings: use std::string instead. If you insist in using C-strings and don't want to play with std::unique() a nicer approach than yours is to use a previous character, initialized to 0 (this can't be part of a C-string, after all):
char previous(0);
for (size_t i(0); ent->d_name[i]; ++i) {
if (ent->d_name[i] != previous) {
switch (previous = ent->d_name[i]) {
...
}
}
}
I hope I understand what you are trying to do, anyway this will find matching pairs and skip over a match.
char c_anotherValue[] = "Hello World!";
int i_len = strlen(c_anotherValue);
for(int i = 0; i < i_len-1;i++)
{
if(c_anotherValue[i] == c_anotherValue[i+1])
{
printf("%c%c",c_anotherValue[i],c_anotherValue[i+1]);
i++;//this will force the loop to skip
}
}
Briefly, I am trying to write a routine that reads comma separated values from a file into a stl vector. This works fine. The values in the csv file might also be in double quotes so I have handled this too by trimming them. However, there is one problem where the values between the quotes might also have commas in them which are not to be treated as delimiters.
If I have a file containing the line
"test1","te,st2","test3","test4"
My file routine reads this into a vector as
"test1"
"te
st2"
"test3"
"test4"
I wrote a routine which I just called PostProcessing. This would go through the vector and correct this problem. It would take each element and check of the first value was a quote. If so it would remove it. It would then look for another quote at the end of the string. If it found one it would just remove it and move onto the next item. If it didn't find one, it would keep going through the vector merging all the following items together until it did find the next quote.
However, this works in merging "te and st2" together into element 2 (index 1) but when I try and erase the required element from the vector it must be failing as the resulting vector output is as follows:
test1
test2
st2"
test3
"test4"
Note also the last element has not been processed because I derement the size of the count but as the vector erase has failed the true count hasn't actually changed.
The PostProcessing code is below. What am I doing wrong?
bool MyClass::PostProcessing()
{
bool bRet = false;
int nCount = m_vecFields.size();
for (int x = 0; x < nCount; x++)
{
string sTemp = m_vecFields[x];
if (sTemp[0] == '"')
{
sTemp.erase(0,1);
if (sTemp[sTemp.size()-1] == '"')
{
sTemp.erase(sTemp.size()-1, 1);
m_vecFields[x] = sTemp;
}
else
{
// find next double quote and merge these vector items
int offset = 1;
bool bFound = false;
while (x+offset < nCount && !bFound)
{
sTemp = sTemp + m_vecFields[x+offset];
if (sTemp[sTemp.size()-1] == '"')
{
// found corresponding "
sTemp.erase(sTemp.size()-1,1);
bFound = true;
}
else
{
offset++;
}
}
if (bFound)
{
m_vecFields[x] = sTemp;
// now remove required items from vector
m_vecFields.erase(m_vecFields.begin()+x+1, m_vecFields.begin()+x+offset);
nCount -= offset;
}
}
}
}
return bRet;
}
Edit: I've spotted a couple of issues with the code which I will be correcting but they don't affect the question being asked.
m_vecFields.erase(m_vecFields.begin()+x+1, m_vecFields.begin()+x+offset);
This function takes a semi-closed interval, which means the "end" of the interval to erase should point one-past the last element to erase. In your case, it points to that element. Change the second argument to m_vecFields.begin()+x+offset+1.
x += offset;
Since you've just processed an item and deleted everything up to the next item, you shouldn't skip offset items here. The x++ from the loop will do just fine.
I need to validate one input string from a user. Eventually it will need to break down into two coordinates. ie a4 c3. And once they are coordinates they need to be broken out into 4 separate ints. a=0 b=1, etc. They must also follow the following stipulations:
If an end-of-input signal is reached the program quits.
Otherwise, all non-alphanumeric characters are discarded from the input.
If what remains is the single letter 'Q'
Then the program quits.
If what remains consists of 4 characters, with one letter and one digit among the first two characters and one letter and one digit among the last two characters, and if each letter-digit pair is in the legal range for our grid
Then input is acceptable.
I have completely over-thought and ruined my function. Please let me know where I can make some corrections.
I am mainly having trouble going from one string, to four chars if and only if the data is valid. Everything else I can handle.
Here is what I have so far.
void Grid::playerMove()
{
string rawMove;
string pair1 = " ";
string pair2 = " ";
bool goodInput = false;
char maxChar = 'a';
char chary1, chary2;
int x11,x22,y11,y22;
for (int i =0; i<size; i++)
{
maxChar++;
}
while(!goodInput)
{
cout<<"What two dots would you like to connect? (Q to quit) ";
cin>>rawMove;
rawMove = reduceWords(rawMove);
if (rawMove == "Q")
{
cout<<"end game";
goodInput = false;
}
else if (rawMove.size() == 4)
{
for(int j=0;j<2;j++)
{
if (pair1[j] >='a' && pair1[j] <=maxChar)
{
chary1 = pair1[j];
}
else if(pair1[j] >=0 && pairl[j]<=size+1)
{
x1 = pair1[j];
}
}
for(int k=0;k<2;k++)
{
if (pair2[k] >='a' && pair2[k] <=maxChar)
{
chary2 = pair2[k];
}
else if(pair2[k] >=0 && pair2[k]<=size+1)
{
x2 = pair2[k];
}
}
}
if(char1 != NULL && char2 != NULL && x1 !=NULL && x2 != NULL)
{
for (int m = 0; m <= size m++)
{
if (char1 == m;)
{
x1 = m;
}
}
for (int n = 0; n <= size n++)
{
if (char2 == n)
{
x2 = n;
}
}
}
}
The end goal would be to have x1, x2, y1, and y2 with their respective values.
Keep in mind I am not allowed to have any external libraries.
It's not clear what exactly you want to achieve, but here are some pointers to get you started:
The while loop will never end because you're setting goodInput to false on quit which lets the loop continue.
The code probably does not even compile? You are missing a curly closing brace..
You are initializing pair1 and pair2 to empty strings but never change them again, so they will never contain any real information about your moves
maybe what you really want is to split up rawMove into the pair1 and pair2 substrings first?
Since this is a homework - and you're supposed to learn from those (right?) - I'm not going to give you the complete answer, but rather something like a recipe:
Use std::istream::getline(char*, std::streamsize s) to read a whole line from std::cin. Make sure you allocate a buffer large enough to hold the expected input (including the terminating null character) plus some more for invalid characters. After the call, check the failbit (input was too long) and the eofbit (hit the end-of-input) of the std::cin stream and handle those cases. Construct a std::string from the buffer if there was no error or EOF has not been reached.
Write a character-classification function (e.g. call it isAlNum(char c)) that returns true if the char argument is alpha-numeric, and false otherwise.
Combine std::string::erase(), std::remove_if(), std::not1(), std::ptr_fun() and your function isAlNum() to sanitise the input string.
Write a function that validates and parses the coordinates from the sanitised input string and call it with the sanitised input string.
Wrap the whole thing in an appropriate while() loop.
This should get you started in the right direction. Of course, if you're allowed to use C++11 features and you know how to write good regular expressions, by all means, use the <regex> header instead of doing the parsing manually.