[Solved] Size of C++ vector is invalid

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Introduction

The C++ vector is a powerful container that allows for dynamic memory allocation and efficient data manipulation. However, it is possible to encounter errors when attempting to use the vector, such as the “Size of C++ vector is invalid” error. This error occurs when the size of the vector is not valid, either because it is too large or too small. In this article, we will discuss the causes of this error and how to solve it.

Solution

The size of a C++ vector is determined by the number of elements it contains. If the size of a vector is invalid, it means that the vector does not contain any elements. To fix this issue, you can add elements to the vector using the push_back() or insert() methods.


From your non-understable question, I can guess that you want the vector to treat the [] operator as “edit if it is exist or create if it is not”. Some thing like the behavior of [] operator in std::map for example..

You simply can not. It was not designed like this.

BTW, you may do something like this: (It is bad idea. Do not.)

int& funky_operator(std::vector<int>& vec, const std::size_t index){
    if(index<vec.size()){
        vec.resize(index+1);
    }
    return vec[index];
}
int main(){
    std::vector<int> intVec;
    intVec.reserve(5);
    funky_operator(intVec,0) = 1;
    std::cout << "intVec Size: " << intVec.size();
}

Again, this is stupid code. Do not use in real life. However, it is what you want.

solved Size of C++ vector is invalid


Solved: Size of C++ Vector is Invalid Code

C++ is a powerful programming language that is used to create a wide variety of applications. One of the most common tasks in C++ is working with vectors, which are collections of data that can be manipulated in various ways. However, when working with vectors, it is important to ensure that the size of the vector is valid. If the size of the vector is invalid, it can lead to errors in the program.

In order to ensure that the size of a vector is valid, it is important to use the correct syntax when declaring the vector. The syntax for declaring a vector in C++ is as follows:

vector<int> myVector(size);

Where “size” is the size of the vector. If the size is not specified, the vector will be created with a size of 0. If the size is specified, but is not a valid number, the vector will not be created and an error will be thrown.

In order to avoid this error, it is important to make sure that the size of the vector is valid before declaring it. This can be done by using the following code:

if (size > 0)
{
    vector<int> myVector(size);
}
else
{
    // Handle the error
}

This code will check to make sure that the size of the vector is valid before creating it. If the size is not valid, the code will handle the error accordingly.

By using the correct syntax and checking the size of the vector before declaring it, it is possible to ensure that the size of the vector is valid and avoid errors in the program.