C Program to Generate All Possible Combinations of List of Numbers

This C program to generate all combination of list of numbers.

Here is the source code of the C program to display all possible combination of list of numbers. The C program is successfully compiled and run on a Linux system. The program output is also shown below.

```
/*
```

 * C program to print all combination of list of numbers

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

/*  Function to generate combination  */

void combinationUtil(int arr[], int data[], int start, int end, int index, int r)

```
{
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```
    int j, i;
```

    // Current combination is ready to be printed, print it

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    if (index == r) {
```
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        for (j = 0; j < r; j++)
```
```
            printf("%d ", data[j]);
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        printf("\n");
```
```
        return;
```
```
    }
```
```
 
```

    // replace index with all possible elements. The condition

    // "end-i+1 >= r-index" makes sure that including one element

    // at index will make a combination with remaining elements

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    // at remaining positions
```

    for (i = start; i <= end && end - i + 1 >= r - index; i++)

```
    {
```
```
        data[index] = arr[i];
```

        combinationUtil(arr, data, i + 1, end, index + 1, r);

```
    }
```
```
}
```
```
/*  End of combinationutil()  */
```
```
 
```

/*  Function to print the combination  */

void printCombination(int arr[], int n, int r)

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{
```
```
    int data[r];
```

    combinationUtil(arr, data, 0, n - 1, 0, r);

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}
```
```
/*  End of printCombination()  */
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```
 
```
```
/*  The main() begins  */
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```
int main()
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```
{
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    int arr[20], r, n, i;
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    printf("Enter the number of input : ");

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    scanf("%d", &n);
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```
    printf("\nEnter the integers: \n");
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    for (i = 0; i < n; i++)
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```
    {
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	scanf("%d", &arr[i]);
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```
    }
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    for (r = 1; r <= 5; r++)
```
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        printCombination(arr, n, r);
```
```
}
```

$ gcc comb_list.c
$ a.out
Enter the number of input : 3
 
Enter the integers: 
1 2 3
1 
2 
3 
1 2 
1 3 
2 3 
1 2 3

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