# How do you find the elements of a pair?

## How do you find the elements of a pair?

To access the elements of the pair, use variable name followed by dot operator followed by the keyword ‘first’ or ‘second’, these are public members of class pair.

## How do you initialize a 2D array?

You can define a 2D array in Java as follows :

1. int[][] multiples = new int[4][2]; // 2D integer array with 4 rows and 2 columns String[][] cities = new String[3][3]; // 2D String array with 3 rows and 3 columns.
2. int[][] wrong = new int[][]; // not OK, you must specify 1st dimension int[][] right = new int[2][]; // OK.

How do you make a 2D array dynamically in C++?

1. // M x N matrix.
2. #define M 4. #define N 5.
3. // Dynamic Memory Allocation in C++ for 2D Array.
4. int main() {
5. // dynamically create array of pointers of size M. int** A = new int*[M];
6. // dynamically allocate memory of size N for each row.

### How do you view a 2D array?

Accessing Elements of Two-Dimensional Arrays Elements in two-dimensional arrays are commonly referred by x[i][j] where ‘i’ is the row number and ‘j’ is the column number. For example: int[][] arr = new int[10][20]; arr[0][0] = 1; The above example represents the element present in first row and first column.

### How do you sort a vector array?

Sorting a vector in C++ can be done by using std::sort(). It is defined in header. To get a stable sort std::stable_sort is used. It is exactly like sort() but maintains the relative order of equal elements.

Is a 2D array a matrix?

An array of arrays is known as 2D array. The two dimensional (2D) array in C programming is also known as matrix. A matrix can be represented as a table of rows and columns.

#### How do you push a 2D vector?

Insertion in Vector of Vectors Elements can be inserted into a vector using the push_back() function of C++ STL. Below example demonstrates the insertion operation in a vector of vectors. The code creates a 2D vector by using the push_back() function and then displays the matrix.

#### What are 2D arrays used for?

A two-dimensional array can also be used to store objects, which is especially convenient for programming sketches that involve some sort of “grid” or “board.” The following example displays a grid of Cell objects stored in a two-dimensional array.

How do you make a pair?

The pair container is a simple container defined in header consisting of two data elements or objects.

1. The first element is referenced as ‘first’ and the second element as ‘second’ and the order is fixed (first, second).
2. Pair is used to combine together two values which may be different in type.

## Is sort in C++ stable?

Yes, it’s as you said, and this is not a concept unique to C++. Stable sorts preserve the physical order of semantically equivalent values. std::sort : The order of equal elements is not guaranteed to be preserved.

## How do you create an array of pairs?

Approach:

1. Traverse the array and select an element in each traversal.
2. For each element selected, traverse the array with help of another loop and form the pair of this element with each element in the array from the second loop.

How do you sort a pair of vectors?

Case 1 : Sorting the vector elements on the basis of first element of pairs in ascending order. This type of sorting can be achieved using simple “ sort() ” function. By default the sort function sorts the vector elements on basis of first element of pairs.

### How do you clear a vector?

Algorithm

1. Run a loop till the size of the vector.
2. Check if the element at each position is divisible by 2, if yes, remove the element and decrement iterator.
3. Print the final vector.

### Is a 2D array a double pointer?

2D array is NOT equivalent to a double pointer! 2D array is “equivalent” to a “pointer to row”. The information on the array “width” (n) is lost.

How do 2D arrays work?

Often data come naturally in the form of a table, e.g., spreadsheet, which need a two-dimensional array. Two-dimensional (2D) arrays are indexed by two subscripts, one for the row and one for the column. Each element in the 2D array must by the same type, either a primitive type or object type.

#### How do you measure a 2D vector?

Print “the 2D vector is:”. for (int i = 0; i < v. size(); i++) for (int j = 0; j < v[i]. size(); j++) print the value of 2D vector v[i][j].

#### How do you declare a 2D vector in C++?

std::vectorvector> array_2d(rows, std::vector(cols, 0)); This creates a rows * cols 2D array where each element is 0. The default value is std::vector(cols, 0) which means each row has a vector which has cols number of element, each being 0. This will create a vector of size k.

What are the types of arrays?

There are three different kinds of arrays: indexed arrays, multidimensional arrays, and associative arrays.

• Creating Indexed Arrays. Indexed arrays store a series of one or more values.
• Creating Multidimensional Arrays.
• Creating Associative Arrays.

## How do you clear a pair in C++?

clear() will clear only the contents of the first vector and not the others. second is a 2d vector and calling p. second. clear() will clear only the contents of the first vector and not the others.

## How do you pass a 2D array into a function?

Passing two dimensional array to a C++ function

1. Specify the size of columns of 2D array void processArr(int a[][10]) { // Do something }
2. Pass array containing pointers void processArr(int *a[10]) { // Do Something } // When callingint *array[10]; for(int i = 0; i < 10; i++) array[i] = new int[10]; processArr(array);

What is a 2D array?

Two dimensional array is an array within an array. It is an array of arrays. In this type of array the position of an data element is referred by two indices instead of one. So it represents a table with rows an dcolumns of data.

### How do you sort a 2D vector?

It is an matrix implemented with the help of vectors. Case 1 : To sort a particular row of 2D vector. This type of sorting arranges a selected row of 2D vector in ascending order . This is achieved by using “sort()” and passing iterators of 1D vector as its arguments.

### How do I sort a 2D array column wise?

Approach: Following are the steps:

1. Sort each row of the matrix.
2. Get transpose of the matrix.
3. Again sort each row of the matrix.
4. Again get transpose of the matrix.

What is a 2D matrix?

A 2D array has a type such as int[][] or String[][], with two pairs of square brackets. The elements of a 2D array are arranged in rows and columns, and the new operator for 2D arrays specifies both the number of rows and the number of columns.

#### How do you declare a vector in a pair C++?

Here you go: #include vector<pair> myVec (N, std::make_pair(-1, -1)); The second argument to that constructor is the initial value that the N pairs will take.

#### How do you find all the possible combinations of an array?

Let the input array be {1, 2, 3, 4, 5} and r be 3. We first fix 1 at index 0 in data[], then recur for remaining indexes, then we fix 2 at index 0 and recur. Finally, we fix 3 and recur for remaining indexes. When number of elements in data[] becomes equal to r (size of a combination), we print data[].

How do you loop a 2D array?

In order to loop over a 2D array, we first go through each row, and then again we go through each column in every row. That’s why we need two loops, nested in each other. Anytime, if you want to come out of the nested loop, you can use the break statement.

## How do you print a 2D array?

Print two dimensional array in Java

1. Arrays. toString() We know that a two dimensional array in Java is a single-dimensional array having another single-dimensional array as its elements.
2. Inner for loop. Naive solution would to use two loops – outer loop for first dimension and inner loop for second dimension of the two dimensional array. import java.

## What is std :: pair?

std::pair is a class template that provides a way to store two heterogeneous objects as a single unit. A pair is a specific case of a std::tuple with two elements. If neither T1 nor T2 is a possibly cv-qualified class type with non-trivial destructor, or array thereof, the destructor of pair is trivial.

How do I return a 2D array in C++?

Use Pointer to Pointer Notation to Return 2D Array From Function in C++ As an alternative, we can use a pointer to pointer notation to return the array from the function. This method has an advantage over others if the objects to be returned are allocated dynamically.