CareerCup

Here we don't have to do actual calculation, else we will never get answer in written test. Think of this as mathematical + logical question. Lets say we have all permutation of 1234. It will be 4! = 24. Now if we look at each column of this list carefully, every number will appear for 6 time.
1234
1324
2134
2314
3124
3214
...

Now if you just concentrate on 4th column, "4" is coming 6 times, same way if we list all number each number will come 6 time in 4th column. So sum of 4th column is (4*6 + 3*6 + 2*6 + 1*6) = 60.

Same way, for all other columns sum would be 60.

Now we are just one step far away from answer. And that is consider "carry". 4th column will give 6 as carry to 3rd columns, again in turn 3rd column will give 6 as carry to 2nd column and so on.

Therefore, final answer would be 66660.

Consider every number as string.
Then sort (descending) them with any sorting method. (Bucket sort can also be used as our string will only contain 0-9)
Once sorted, append each string in order to result string.
Convert result string to number again, which is nothing but maximum possible number.

E.G. {21,9,23} -> {"21","9","23"} ->{"9","23","21"} -> {"92321"} -> 92321

#include <stdio.h>
#include <stdlib.h>
#define SIZEOF(a) sizeof(a) / sizeof((a)[0])

char order[26];

void generateOrder(char dict[])
{
    int i=0;
    for(i=0;i<26;i++)
    {
        order[ dict[i] - 'a' ] = i;
    }
}
int position(char x)
{
    return order[x-'a'];
}
int compare(void *a,void *b)
{
    return position( *(char *)a) -  position (*(char *)b );
}
int main(void) {
    
	char dict[26] = {      'p','a','b','d','e',
                           'f','g','h','i','j',
                           'k','l','m','n','o',
                           'c','q','r','s','t',
                           'u','v','w','x','y',
                           'z'};
	
    
    generateOrder(dict);
    
    char str[6] = "sheep";
    qsort(str,SIZEOF(str),sizeof(char),compare);
    printf("%s",str);
	return 0;
}

Just one line code ... !!!

/*
int num=123;
char dest[10];
*/

sprintf(dest,"%d",num);