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A Practical Guide to 2D Vectors in C++
Including the Vector Header File
To use vectors in C++, you need to include the appropriate header files at the beginning of your program. For 2D vectors, we typically use:
Alternatively, you can include all the necessary Standard Template Libraries (STL) at once using the following command:
#include<bits/stdc++.h>
Initialization of 2D Vectors in C++
There are different ways to initialize 2D vectors in C++, and two common methods are explained below.
1. Initialization with Known Elements
#include
#include
using namespace std;
int main(){
vector<vector> v {{1, 0, 1}, {0, 1}, {1, 0, 1}};
for(int i=0; i<v.size(); i++){
for(int j=0; j<v[i].size(); j++)
cout << v[i][j] << " ";
cout << endl;
}
}
Output:
1 0 1
0 1
1 0 1
Each value within the curly braces, such as `{1, 0, 1}` and `{0, 1}`, represents an individual vector within the 2D vector.
2. Initialization with Specified Size
#include
#include
using namespace std;
int main(){
int num_col = 3; // Number of columns
int num_row = 4; // Number of rows
vector row(num_col, 0); // Initialize a single row
vector<vector> v(num_row, row); // Initialize the 2D vector
for(int i=0; i<v.size(); i++){
for(int j=0; j<v[i].size(); j++)
cout << v[i][j] << " ";
cout << endl;
}
}
Output:
0 0 0
0 0 0
0 0 0
0 0 0
In this code, first, a one-dimensional vector `row` is created, representing each row of the 2D vector. Then, the entire 2D vector is initialized by repeating this row.
A shorter way to achieve the same result is:
#include
#include
using namespace std;
int main(){
int num_col = 3; // Number of columns
int num_row = 4; // Number of rows
vector<vector> v(num_row, vector(num_col, 0)); // Initialize the 2D vector
for(int i=0; i<v.size(); i++){
for(int j=0; j<v[i].size(); j++)
cout << v[i][j] << " ";
cout << endl;
}
}
Using Iterators for 2D Vectors
#include
#include
using namespace std;
int main(){
vector<vector> v {{1, 0, 1}, {0, 1}, {1, 0, 1}};
// Iterator for the 2D vector
vector<vector>::iterator it1;
// Iterator for each vector within the 2D vector
vector::iterator it2;
// Traverse a 2D vector using iterators
for(it1 = v.begin(); it1 != v.end(); it1++){
for(it2 = it1->begin(); it2 != it1->end(); it2++)
cout << *it2 << " ";
cout << endl;
}
}
Output:
1 0 1
0 1
1 0 1
Iterators are particularly useful for operations where precise positioning within the vector is required.
Manipulating 2D Vectors
Adding Elements
// Initialize the 2D vector
vector<vector> v;
v.push_back({1, 0, 1});
v.push_back({0, 1});
v.push_back({1, 0, 1});
]
Removing Elements
// Initialize the 2D vector
vector<vector> v;
v.push_back({1, 0, 1});
v.push_back({0, 1});
v.push_back({1, 0, 1});
Removing Elements
// Remove the last vector from a 2D vector
v.pop_back();
// Remove the second vector from a 2D vector
v.erase(it + 1);
To remove all vectors from the 2D vector, you can use the `clear()` function.
Conclusion
2D vectors in C++ are a versatile tool ideal for working with two-dimensional data structures like matrices and tables. Understanding their initialization, iteration, and manipulation is essential for solving problems that require such structures. We hope this guide has helped you with using 2D vectors in C++. Feel free to ask questions or leave comments for further clarification on this topic.
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