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I Keep getting this error when I try to set the first char in firstname and lastname to a null and return it to a 1.
my code is...
int DeregisterStudent(int SID, struct studentdata SRecord[])
{
int index;
index = SRecordSearch(SID, MAXRECS, SRecord);
if(index >= 0)
{
SRecord[index].sid = 0;
SRecord[index].lastname = '\0';
SRecord[index].firstname = '\0';
return 1;
}
return 0;
}
and the error I get is error:incompatible type in assignment
for these two lines
SRecord[index].lastname = '\0';
SRecord[index].firstname = '\0';
You are not writing to the string correctly, it should be
SRecord[index].lastname[0] = '\0';
or
SRecord[index].lastname = "";
depending on how the struct was declared. In the second case you might be overwriting a dynamically allocated string pointer, in which case it should be free()ed.
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string longestCommonPrefix(vector<string>& strs) {
string res = "";
int i, j;
bool flag = true;
for(int i=0; i<strs[0].size(); i++)
{
for(int j=0; j<strs.size()-1; j++)
{
if(strs[j][i] == strs[j+1][i])
{
flag = true;
}
else
return res;
}
if(flag == true)
{
res += strs[0][i];
}
}
return res;
}
I was doing this leetcode question where we had to find the longest common prefix of given array of strings and then i got stuck at this i cant understand what is the meaning of this error, most of the test cases are passed so i don't think logic is wrong.Is there any corner cases i am missing?
Runtime Error Message:
Line 924: Char 9: runtime error: reference binding to null pointer of type 'std::__cxx11::basic_string, std::allocator >' (stl_vector.h)
Last executed input:
[]
Thanks in advance
Its null pointer exception. So you should check if str is null i.e. str=='" for each string in vector.
and return answer accordingly.
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The problem is that in my code (which there is a loop getting alphabets of a string) it can not save the current string input into another variable:
Here is the code:
if(isalpha(Str[i])){
while (isalpha(Str[i])){
i++;
}
Str.erase( 0, i);
return 0;
}
I want to have another string (like temp ) to save each alphabet into the while loop. something like this:
if(isalpha(Str[i])){
string temp;
while (isalpha(Str[i])){
temp[i]=Str[i];
i++;
}
Str.erase( 0, i);
return 0;
}
can anyone help that what is the problem here?
As you declare temp as 0 length string, using temp[i] would be undefined behavior.
You may solve this problem by using
temp.push_back(Str[i]);
instead of
temp[i]=Str[i];
You're passing a position and count to std::string::erase. You can use the same parameters to construct another string with the characters that are about to be erased.
while (isalpha(Str[i])) {
i++;
}
string temp(Str, 0, i);
Str.erase(0, i);
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Is there another solution, please?
if(!http_piconpath && http_tpl)
{ http_piconpath = http_tpl; }
If not exist http_piconpath but exist http_tpl then assign the value from http_tpl to http_piconpath.
You provide very little information about what you are doing. Assuming that you use strings from your comment, the if statement you've got is not valid for strings, you'll see your compiler screaming that it can't convert string to bool. Below is a very basic example. Note that you must initialise http_piconpath, else it will have a garbage value and you won't know if its value is set or not.
#include <iostream>
#include <string>
using namespace std;
int main()
{
string http_piconpath = "";
string http_tpl = "string";
if(http_piconpath == "" && http_tpl != "") {
http_piconpath = http_tpl;
}
cout << http_piconpath << endl;
return 0;
}
Supposing that both are pointers (of compatible types),
if(!http_piconpath) http_piconpath = http_tpl;
Or
http_piconpath = http_piconpath ? http_piconpath : http_tpl;
If picon is null, it gets the value of tpl; if both are null, nothing changes.
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The variable steady_counter is intialized as a constant integer.
cout << steady_counter;
So long as i have the above statement anywhere before the following code, the function runs as expected and checks if an integer input is or is not a runaround number.
The problem is that when the cout line is not present, the constant integer changes within the below if statements. I tested this by printing steady_counter before entering the if-else, and then after the if-else.
Without the cout line, steady_counter changes to a 4 digit number.
for (int i = 0; i < 10; i++)
{
if (CheckArr[i])
{
num_of_unique++;
}
}
if ((steady_counter == num_of_unique) & (final == NumArr[0]) )
{
return true;
}
else
{
return false;
}
}
Any idea what's going on? Why do I require a cout line to maintain the constant integer steady_counter?
One obvious problem:
for (int i = counter; i > 0; i --)
NumArr[i] = -1;
This covers values from 1 to counter inclusive; while valid indexes for NumArr are from 0 to counter-1 inclusive. So you write outside the array, corrupting something else; possibly another local variable.
Either correct the off-by-one error in the index
NumArr[i-1] = -1;
or use a more canonical loop
for (int i = 0; i < counter; ++i)
or, for more of a C++ flavour,
std::fill(NumArr, NumArr+counter, -1);
There are likely to be further errors, which are better found by using your debugger than by asking people to read through all your code.
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I have map<string, inode_ptr> directories
I want to retrieve the value associated with a certain key.
so I did this: inode_ptr i = directories.find("string");
But it is returning the string key, what should I do?
Use the following approach
inode_ptr i = NULL;
auto it = directories.find("string");
if ( it != directories.end() ) i = it->second;
Maybe it is even better to write
inode_ptr i = {};
instead of
inode_ptr i = NULL;
Give this a go:
inode_ptr myInode = NULL;
map<string, inode_ptr>::iterator i = directories.find("string");
if ( i != directories.end() )
{
myInode = i->second;
}
else
{
cerr << "no 'String' in the map, I should be "
<< "sure to check for null before using myInode" << endl;
}
Here is a link to that fine manual referenced in the above comments:
http://www.cplusplus.com/reference/map/map/find/