Permutation of a String in C

This is a C program to permute all the letters of an input string.

This algorithm finds all permutations of the letters of a given string. It is a recursive algorithm using concept of backtracking.

Here is the source code of the C program to permute all letters of an input string. The C program is successfully compiled and run on a Linux system. The program output is also shown below.

```
/*
```

 * C program to find all permutations of letters of a string

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

/* Function to swap values at two pointers */

```
void swap (char *x, char *y)
```
```
{
```
```
    char temp;
```
```
    temp = *x;
```
```
    *x = *y;
```
```
    *y = temp;
```
```
}
```
```
/*  End of swap()  */
```
```
 
```

/*  Function to print permutations of string  */

```
void permute(char *a, int i, int n)
```
```
{
```
```
    int j;
```
```
    if (i == n)
```
```
        printf("%s\n", a);
```
```
    else {
```
```
        for (j = i; j <= n; j++)
```
```
        {
```
```
            swap((a + i), (a + j));
```
```
            permute(a, i + 1, n);
```

            swap((a + i), (a + j)); //backtrack

```
        }
```
```
    }
```
```
}
```
```
 
```
```
/*  The main() begins  */
```
```
int main()
```
```
{
```
```
    char a[20];
```
```
    int n;
```
```
    printf("Enter a string: ");
```
```
    scanf("%s", a);
```
```
    n = strlen(a);
```
```
    printf("Permutaions:\n"); 
```
```
    permute(a, 0, n - 1);
```
```
    getchar();
```
```
    return 0;
```
```
}
```

$ gcc permute.c -o permute
$ ./permute
 
Enter a string: SAN
 
All possible permutations are:
    SAN
    SNA
    ASN
    ANS
    NAS
    NSA

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