﻿ C : Find all possible combinations of r elements in an array

# C Exercises: Print all possible combinations of r elements in a given array

## C Array: Exercise-82 with Solution

Write a program in C to print all possible combinations of r elements in a given array.

Expected Output:
The given array is:
1 5 4 6 8 The combination from by the number of elements are: 3
The combinations are:
1 5 4 6
1 5 4 8
1 5 6 8
1 4 6 8
5 4 6 8

The task is to write a C program that prints all possible combinations of r elements from a given array. The program should generate and display each unique combination of the specified number of elements. The output should list all the possible combinations formed from the array elements for the given value of r.

Sample Solution:

C Code:

``````#include <stdio.h>

// Function to generate combinations
void makeCombination(int arr1[], int data[], int st, int end, int index, int r);

// Function to display combinations
void CombinationDisplay(int arr1[], int n, int r) {
int data[r]; // Temporary array to store the combination
makeCombination(arr1, data, 0, n - 1, 0, r); // Generate combinations
}

// Recursive function to generate combinations
void makeCombination(int arr1[], int data[], int st, int end, int index, int r) {
// Base case: if index equals r, print the combination
if (index == r) {
for (int j = 0; j < r; j++)
printf("%d ", data[j]); // Print the combination elements
printf("\n"); // Move to the next line for the next combination
return;
}

// Generate combinations recursively
for (int i = st; i <= end && end - i + 1 >= r - index; i++) {
data[index] = arr1[i]; // Fill data[] with elements of arr1[] for the current combination
makeCombination(arr1, data, i + 1, end, index + 1, r); // Recursively generate combinations
}
}

int main() {
int arr1[] = {1, 5, 4, 6, 8};
int r = 4; // Number of elements in each combination
int n = sizeof(arr1) / sizeof(arr1[0]); // Calculate array size
int i;

// Printing the original array
printf("The given array is:  \n");
for (i = 0; i < n; i++) {
printf("%d  ", arr1[i]);
}
printf("\n");

printf("The combination from by the number of elements are: %d\n", r);
printf("The combinations are: \n");
CombinationDisplay(arr1, n, r); // Display combinations
return 0;
}
```
```

Output:

```The given array is:
1  5  4  6  8
The combination from by the number of elements are: 4
The combinations are:
1 5 4 6
1 5 4 8
1 5 6 8
1 4 6 8
5 4 6 8
```

Visual Presentation:

Flowchart 1:

Flowchart 2:

C Programming Code Editor:

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