Vector Operations in C++

Advanced Vector Operations in C++.

IntermediateSTL Containers ProgramsExample 2 of 10

vector-operations.cpp

1#include <iostream>
2#include <vector>
3#include <algorithm>
4using namespace std;
5
6int main() {
7    vector<int> vec = {5, 2, 8, 1, 9, 3};
8    
9    cout << "Original vector: ";
10    for (int num : vec) {
11        cout << num << " ";
12    }
13    cout << endl;
14    
15    // Sort vector
16    sort(vec.begin(), vec.end());
17    cout << "Sorted vector: ";
18    for (int num : vec) {
19        cout << num << " ";
20    }
21    cout << endl;
22    
23    // Reverse vector
24    reverse(vec.begin(), vec.end());
25    cout << "Reversed vector: ";
26    for (int num : vec) {
27        cout << num << " ";
28    }
29    cout << endl;
30    
31    // Find element
32    auto it = find(vec.begin(), vec.end(), 5);
33    if (it != vec.end()) {
34        cout << "Element 5 found at index: " << distance(vec.begin(), it) << endl;
35    }
36    
37    // Insert element
38    vec.insert(vec.begin() + 2, 100);
39    cout << "\nAfter inserting 100 at index 2: ";
40    for (int num : vec) {
41        cout << num << " ";
42    }
43    cout << endl;
44    
45    // Erase element
46    vec.erase(vec.begin() + 2);
47    cout << "After erasing element at index 2: ";
48    for (int num : vec) {
49        cout << num << " ";
50    }
51    cout << endl;
52    
53    // Clear vector
54    vec.clear();
55    cout << "\nSize after clear: " << vec.size() << endl;
56    cout << "Is empty: " << (vec.empty() ? "Yes" : "No") << endl;
57    
58    return 0;
59}

Output

Original vector: 5 2 8 1 9 3
Sorted vector: 1 2 3 5 8 9
Reversed vector: 9 8 5 3 2 1
Element 5 found at index: 2

After inserting 100 at index 2: 9 8 100 5 3 2 1
After erasing element at index 2: 9 8 5 3 2 1

Size after clear: 0
Is empty: Yes

What's going on

The program demonstrates advanced vector operations:

Sorting elements using sort()

Reversing vector using reverse()

Finding elements using find()

Inserting elements at specific positions

Erasing elements from vector

Clearing entire vector

These operations enable powerful vector manipulation.

Header Files Used

1.#include <iostream>

Provides cout and cin for input/output operations.

2.#include <vector>

Provides vector container class.

3.#include <algorithm>

Provides algorithms like sort(), reverse(), find().

Understanding Vector Operations

Operation Types

Sorting: arrange elements in order

Reversing: reverse element order

Finding: locate specific element

Inserting: add element at position

Erasing: remove element at position

Clearing: remove all elements

Iterators

begin(): points to first element

end(): points past last element

Used for range operations

Sorting Vector

Using sort()

sort(vec.begin(), vec.end());

How it works

Sorts elements in ascending order

Uses iterators to specify range

Modifies original vector

O(n log n) time complexity

Example

{5, 2, 8, 1, 9, 3} → {1, 2, 3, 5, 8, 9}

Reversing Vector

Using reverse()

reverse(vec.begin(), vec.end());

How it works

Reverses order of elements

First becomes last, last becomes first

Uses iterators for range

O(n) time complexity

Example

{1, 2, 3, 5, 8, 9} → {9, 8, 5, 3, 2, 1}

Finding Elements

Using find()

auto it = find(vec.begin(), vec.end(), 5);

How it works

Searches for value in range

Returns iterator to found element

Returns end() if not found

O(n) time complexity (linear search)

Checking Result

if (it != vec.end()) {

int index = distance(vec.begin(), it);

} else {

// Element not found

}

1// Element found

Inserting Elements

Using insert()

vec.insert(vec.begin() + 2, 100);

How it works

Inserts element at specified position

Shifts existing elements

Expensive for large vectors (O(n))

Position specified using iterator

Example

Before: {9, 8, 5, 3, 2, 1}

After insert at index 2: {9, 8, 100, 5, 3, 2, 1}

Erasing Elements

Using erase()

vec.erase(vec.begin() + 2);

How it works

Removes element at specified position

Shifts remaining elements

Expensive for large vectors (O(n))

Position specified using iterator

Example

Before: {9, 8, 100, 5, 3, 2, 1}

After erase at index 2: {9, 8, 5, 3, 2, 1}

Clearing Vector

Using clear()

vec.clear();

How it works

Removes all elements

Size becomes 0

Capacity may remain (implementation dependent)

O(n) time complexity

Checking Empty

vec.empty() // Returns true if size is 0

When to Use These Operations

Best For

Sorting: when order matters

Reversing: when reverse order needed

Finding: searching for specific values

Inserting: adding at specific positions

Erasing: removing specific elements

Clearing: resetting vector

Performance Considerations

insert()/erase(): expensive (O(n))

Use sparingly for large vectors

Prefer push_back()/pop_back() when possible

Consider other containers for frequent insert/erase

Important Considerations

Iterators

begin(): first element

end(): past last element

Used for range operations

Can be incremented/decremented

Performance

sort(): O(n log n)

reverse(): O(n)

find(): O(n)

insert()/erase(): O(n)

clear(): O(n)

Modifying Operations

Most operations modify original vector

Make copies if original needed

Be careful with iterator invalidation

return 0;

This ends the program successfully.

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