2D Vector - Remove Rows by search - c++

Question

I'm quite new to vector and need some additional help with regards to vector manipulation.
I've currently created a global StringArray Vector that is populated by string values from a text file.
typedef std::vector<std::string> StringArray;
std::vector<StringArray> array1;
I've created a function called "Remove" which takes the input from the user and will eventually compare the input against the first value in the array to see whether it's a match. If it is, the entire row will then deleted and all elements beneath the deleted row will be "shuffled up" a position to fill the game.
The populated array looks like this:
Test1 Test2 Test3
Cat1 Cat2 Cat3
Dog1 Dog2 Dog3
And the remove function looks like this:
void remove()
{
string input;
cout << "Enter the search criteria";
cin >> input;
I know that I will need a loop to iterate through the array and compare each element with the input value and check whether it's a match.
I think this will look like:
for (int i = 0; i < array1.size(); i++)
{
for (int j = 0; j < array1[i].size(); j++)
{
if (array1[i] = input)
**//Remove row code goes here**
}
}
But that's as far as I understand. I'm not really sure A) if that loop is correct and B) how I would go about deleting the entire row (not just the element found). Would I need to copy across the array1 to a temp vector, missing out the specified row, and then copying back across to the array1?
I ultimately want the user to input "Cat1" for example, and then my array1 to end up being:
Test1 Test2 Test3
Dog1 Dog2 Dog3
All help is appreciated. Thank you.

Answer 1

So your loop is almost there. You're correct in using one index i to loop through the outer vector and then using another index j to loop through the inner vectors. You need to use j in order to get a string to compare to the input. Also, you need to use == inside your if statement for comparison.
for (int i = 0; i < array1.size(); i++)
{
for (int j = 0; j < array1[i].size(); j++)
{
if (array1[i][j] == input)
**//Remove row code goes here**
}
}
Then, removing a row is the same as removing any vector element, i.e. calling array1.erase(array1.begin() + i); (see How do I erase an element from std::vector<> by index?)

Answer 2

Use std::list<StringArray> array1;
Erasing an item from an std::vector is less efficient as it has to move all the proceeding data.
The list object will allow you to remove an item (a row) from the list without needing to move the remaining rows up. It is a linked list, so it won't allow random access using a [ ] operator.

Answer 3

You can use explicit loops, but you can also use already implemented loops available in the standard library.
void removeTarget(std::vector<StringArray>& data,
const std::string& target) {
data.erase(
std::remove_if(data.begin(), data.end(),
[&](const StringArray& x) {
return std::find(x.begin(), x.end(), target) != x.end();
}),
data.end());
}
std::find implements a loop to search for an element in a sequence (what you need to see if there is a match) and std::remove_if implements a loop to "filter out" elements that match a specific rule.
Before C++11 standard algorithms were basically unusable because there was no easy way to specify custom code parameters (e.g. comparison functions) and you had to code them separately in the exact form needed by the algorithm.
With C++11 lambdas however now algorithms are more usable and you're not forced to create (and give a reasonable name to) an extra global class just to implement a custom rule of matching.