CS1101C Lab 1 (Even Week)

Swapping Digits

The name of your C program file must be called swap1.c, files with any other name will not be marked.

Preliminary

Example

If I swap the digits in position 1 and position 2, the result is the four-digit number 6578.

If I swap the digits in position 3 and position 4, the result is the four-digit number 5687.

If I swap the digits in position 4 and position 2, the result is the four-digit number 5876.

If I swap the digits in position 3 and position 3, the result is the four-digit number 5678. There is no change since the position numbers are the same.

Your Task

Template

/**********************************************************************/
/* Matric Number: U061234A and U069876B                               */
/* Userid: u0601234 and u0609876                                      */
/* (For those doing pair programming, only ONE of you should submit   */
/*  your program. The other student should NOT submit.)               */
/* Lab: 1                                                             */
/* Lab Group Number: 99                                               */
/* Lab TA's Name: Who needs a lab TA when you're Bill Gates?          */
/* Lab Session Date: 14 February 2007                                 */
/* Lab Session Time: 1000 - 1145                                      */
/* Title: Digit swapping.                                             */
/* Purpose: Perform digit swapping.                                   */
/**********************************************************************/

#include <stdio.h>
#include <math.h>

int main(void)
{
    /* Variable declaration.                     */
    /* You can declare any other variables here. */
    int input, pos1, pos2, output;

    /* Get user input. Do not change this. */
    printf("Enter a four-digit number (0 - 9999): ");
    scanf("%d", &input);
    printf("Enter position one to swap (1 - 4): ");
    scanf("%d", &pos1);
    printf("Enter position two to swap (1 - 4): ");
    scanf("%d", &pos2);

    /* Compute result. Type your code here. */

    /* Print result. Do not change this. */
    printf("The output is: %04d\n", output);

    return 0;
}

Sample Runs

$ gcc -Wall -lm swap1.c -o swap1
$ ./swap1
Enter a four-digit number (0 - 9999): 7536
Enter position one to swap (1 - 4): 4
Enter position two to swap (1 - 4): 1
The output is: 6537

$ ./swap1
Enter a four-digit number (0 - 9999): 0825
Enter position one to swap (1 - 4): 1
Enter position two to swap (1 - 4): 3
The output is: 2805

$ ./swap1
Enter a four-digit number (0 - 9999): 7940
Enter position one to swap (1 - 4): 4
Enter position two to swap (1 - 4): 1
The output is: 0947

$ ./swap1
Enter a four-digit number (0 - 9999): 0000
Enter position one to swap (1 - 4): 2
Enter position two to swap (1 - 4): 2
The output is: 0000

$

Points to Note

• For simplicity, we assume that user input will always be within the range of permissible values, so there is no need to perform any explicit checks on the data entered by the user. You may assume that the four-digit number is always an integer between 0 to 9999 inclusive, and the positions are always integers between 1 to 4 inclusive.
• Do not use any other data types except int. That means you are not allowed to use double, float, char, etc. You are only allowed to use the int data type and nothing else.
• The only conversion specifier allowed within the scanf and printf statements is strictly %d. Do not the %i conversion specifier.
• Do not use any logical (&&, ||, !) or bit-wise (&, |, ^, !, <<, >>) operators.
• Do not use any selection statements (if, if-else, switch), repetition statements (while, do-while, for), nor the conditional operator "?:".
• Do not use any functions from the math library. The only exception is the pow function which you are allowed to use.

Ponder

1. Why do we use %d instead of %i in the scanf statements?
2. Why do we use %04d in the printf statement?

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