1999 LSU Computer Science High School Programming Contest
Novice and Veteran Problem 1
How does ET count?

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Problem Statement

Many experts believe that humans settled on base ten (decimal) because we have ten fingers. The Searchers for Extra Terrestrials (SET) is convinced we that they will find life soon. They are also concerned that the life they discover will not have ten digits (and hence not use base ten). They have hired you to write a program to convert numbers in various bases to base ten.

Your input will be in the following format:

Valid bases are from base 2 to base 16.

If the values 10 through 15 are needed, you will use the letters "a" through "f" respectively. You will stop when you read in 0 for the base.

Example Input: 

4 
123
8 
173
16 
12a3
16
ff
0

Your output should look like:

123 (4) is 27
173 (8) is 123
12a3 (16) is 4771
ff (16) is 255

NOTE: Do not worry about the formatting of numeric output (leading/trailing spaces around numbers are acceptable).

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Clarifications:






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Source Code for a Solution to this Problem

// preprocessor directives
#include <stdio.h>
#include <string.h>

#define QUIT 0

// function prototypes
int power(int base, int exponent);
void convert_to_int(char num[], int converted[], int *len);

int main(void)
{
    int base,i,length;
    int converted[256];
    char num_ary[256];

   scanf("%d %s",&base,num_ary);
   while( QUIT != base)
    {
        if( 1 == base)
         printf("We were not to test for base 1.\n");
        else
         {
            convert_to_int(num_ary,converted,&length);

            converted[length] = 0;
            //get decimal value
            for(i=0; i < length; i++)
              converted[length] += converted[i] * power(base,i);

            printf("%s (%d) is %d.\n",num_ary,base,converted[length]);

         } // else

            scanf("%d %s",&base,num_ary);

    }//while

   return 0;

}

/*  converts the char string to an integer array representing
    the base 10 digit for each place value.
    Needs this due to the 'a' through 'f' values in bases
    larger than 10
*/

void convert_to_int(char num[],int conv[],int *n)
{
  int i,j;

//  gives the length of the string contained in num
  *n = strlen(num);

  for(i=0, j = *n - 1; i < *n; i++,j--)
  {
    if( num[i] < 'a')
      conv[j] = num[i] - 48;  //ascii of digit - 48 gives int value
    else
     conv[j] = num[i] - 87;  //ascii of char - 87 gives int value for a to f


  } //end of for

} // end of convert_to_int


/* function power is an integer version of C's function
   accepts a base and exponent and gives the value of the
   base raised to the exponent
*/
int power(int base, int exp)
{
   int i, sum = 1;

     for(i = 1; i <= exp; i++)
      sum *= base;

   return sum;
} // end power

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Sample Input

4
123
8
173
16
12a3
16
ff
0

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Sample Output

123 (4) is 27.
173 (8) is 123.
12a3 (16) is 4771.
ff (16) is 255.

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Judge Data Set 1 - Input

2
10
3
10
4
10
5
10
6
10
7
10
8
10
9
10
10
10
11
10
12
10
13
10
14
10
15
10
16
10
4
123
8
173
16
12a3
11
32a1a
13
aab1c
2
101011
10
12904
3
2121021
8
31
10
0
3
0
16
0
0

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Judge Data Set 1 - Output

10 (2) is 2.
10 (3) is 3.
10 (4) is 4.
10 (5) is 5.
10 (6) is 6.
10 (7) is 7.
10 (8) is 8.
10 (9) is 9.
10 (10) is 10.
10 (11) is 11.
10 (12) is 12.
10 (13) is 13.
10 (14) is 14.
10 (15) is 15.
10 (16) is 16.
123 (4) is 27.
173 (8) is 123.
12a3 (16) is 4771.
32a1a (11) is 47816.
aab1c (13) is 309464.
101011 (2) is 43.
12904 (10) is 12904.
2121021 (3) is 1897.
31 (8) is 25.
0 (10) is 0.
0 (3) is 0.
0 (16) is 0.

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Judge Data Set 2 - Input

15
abcde
2
111
3
1
11
12349a
10
256
2
111111
9
123480
2
10
2
10
3
10
4
10
5
10
6
10
7
10
8
10
9
10
10
10
11
10
12
10
13
10
14
10
15
10
16
10
0

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Judge Data Set 2 - Output

abcde (15) is 546284.
111 (2) is 7.
1 (3) is 1.
12349a (11) is 194919.
256 (10) is 256.
111111 (2) is 63.
123480 (9) is 74754.
10 (2) is 2.
10 (2) is 2.
10 (3) is 3.
10 (4) is 4.
10 (5) is 5.
10 (6) is 6.
10 (7) is 7.
10 (8) is 8.
10 (9) is 9.
10 (10) is 10.
10 (11) is 11.
10 (12) is 12.
10 (13) is 13.
10 (14) is 14.
10 (15) is 15.
10 (16) is 16.


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The statements and opinions included in these pages are those of the LSU High School Programming Contest Staff only. Any statements and opinions included in these pages are not those of Louisiana State University or the LSU Board of Supervisors.
© 1999 LSU High School Programming Contest

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