How to Remove Item at a Specific Index from a Vector in C++

How to Remove Item at a Specific Index from a Vector in C++ ?

Answer

To remove an item at a specific index from a vector in C++, you can use the erase method of the std::vector class.


✐ Examples

1 Remove Item at Specific Index Using erase Method

In this example,

  1. We start by including the necessary headers: <vector> and <iostream>.
  2. We create a vector named vec and initialize it with some integer values.
  3. We specify the index of the item we want to remove and store it in a variable named index_to_remove.
  4. We use the erase method to remove the item at the specified index. The erase method takes an iterator pointing to the element to be removed.
  5. We obtain the iterator by calling vec.begin() + index_to_remove and pass it to the erase method.
  6. Finally, we print the modified vector to standard output to see the result.

C++ Program

#include &lt;vector&gt;
#include &lt;iostream&gt;

int main() {
    std::vector&lt;int&gt; vec = {10, 20, 30, 40, 50};
    int index_to_remove = 2;
    vec.erase(vec.begin() + index_to_remove);
    std::cout &lt;&lt; "Vector after removing the item at index " &lt;&lt; index_to_remove &lt;&lt; ": ";
    for (int val : vec) {
        std::cout &lt;&lt; val &lt;&lt; " ";
    }
    std::cout &lt;&lt; std::endl;
    return 0;
}

Output

Vector after removing the item at index 2: 10 20 40 50

2 Remove Item at Specific Index Using custom function

In this example,

  1. We start by including the necessary headers: <vector> and <iostream>.
  2. We define a function named remove_at_index that takes a reference to a vector and an index as parameters.
  3. Inside the function, we check if the index is valid (i.e., within the bounds of the vector).
  4. If the index is valid, we use the erase method to remove the item at the specified index, obtaining the iterator by calling vec.begin() + index and passing it to the erase method.
  5. We create a vector named vec and initialize it with some integer values.
  6. We specify the index of the item we want to remove and store it in a variable named index_to_remove.
  7. We call the remove_at_index function, passing vec and index_to_remove as arguments.
  8. Finally, we print the modified vector to standard output to see the result.

C++ Program

#include &lt;vector&gt;
#include &lt;iostream&gt;

void remove_at_index(std::vector&lt;int&gt; &vec, int index) {
    if (index >= 0 && index &lt; vec.size()) {
        vec.erase(vec.begin() + index);
    }
}

int main() {
    std::vector&lt;int&gt; vec = {10, 20, 30, 40, 50};
    int index_to_remove = 2;
    remove_at_index(vec, index_to_remove);
    std::cout &lt;&lt; "Vector after removing the item at index " &lt;&lt; index_to_remove &lt;&lt; ": ";
    for (int val : vec) {
        std::cout &lt;&lt; val &lt;&lt; " ";
    }
    std::cout &lt;&lt; std::endl;
    return 0;
}

Output

Vector after removing the item at index 2: 10 20 40 50

Summary

In this tutorial, we learned How to Remove Item at a Specific Index from a Vector in C++ language with well detailed examples.


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