Week 02 Extra Sample Solutions

Information

This page contains extra exercises for week 02.
These exercises are not compulsory, nor do they provide any marks in the course.
You cannot submit any of these exercises, however autotests are available for them (Command included at bottom of each exercise).

Exercise
(●◌◌)
:
Ordering Three Integers

Write a C program order3.c using if statements (no loops) that reads 3 integers and prints them from smallest to largest.

Examples

dcc order3.c -o order3
./order3
Enter integer: 23
Enter integer: 5
Enter integer: 27
The integers in order are: 5 23 27
./order3
Enter integer: 3
Enter integer: 6
Enter integer: 27
The integers in order are: 3 6 27
./order3
Enter integer: 9
Enter integer: 8
Enter integer: 7
The integers in order are: 7 8 9

You can assume the user supplies 3 integers. You do not have to check the return value from scanf.

When you think your program is working, you can use autotest to run some simple automated tests:

1091 autotest order3

Sample solution for order3.c

// Modified 3/3/2018 by Andrew Taylor (andrewt@unsw.edu.au)
// as a lab example for COMP1511

// Print 3 integers in non-decreasing order

#include <stdio.h>

int main(void) {
    int a, b, c;
    int tmp;

    printf("Enter integer: ");
    if (scanf("%d", &a) != 1) {
        return 1; // EXIT_FAILURE would be more portable
    }

    printf("Enter integer: ");
    if (scanf("%d", &b) != 1) {
        return 1;
    }

    printf("Enter integer: ");
    if (scanf("%d", &c) != 1) {
        return 1;
    }

    // a, b, c can be in any order

    // swap a & b if they are not in order
    if (a > b) {
        tmp = b;
        b = a;
        a = tmp;
    }

    // swap a & c if they are not in order
    if (a > c) {
        tmp = c;
        c = a;
        a = tmp;
    }

    // a must be the smallest now

    // swap b & c if they are not in order
    if (b > c) {
        tmp = c;
        c = b;
        b = tmp;
    }

    // a, b, c now in  order

    printf("The integers in order are: %d %d %d\n", a, b, c);

    return 0;
}

Alternative solution for order3.c

// Program to take in three numbers then print them
// in decreasing order.
// Written by Rory Golledge (12/06/2021)
//
// Note: This solution provides an alternative to the much
// "smarter" solution given. This is in the case that a student
// does not understand the other as it may seem less
// intuitive.

#include <stdio.h>

int main(void) {
    int a;
    int b;
    int c;

    // Scan in all numbers
    printf("Enter integer: ");
    scanf("%d", &a);

    printf("Enter integer: ");
    scanf("%d", &b);

    printf("Enter integer: ");
    scanf("%d", &c);

    printf("The integers in order are: ");

    // Determine order from 6 possible combinations
    // and print them out.
    if (a <= b && b <= c) {
        printf("%d %d %d\n", a, b, c);
    } else if (a <= c && c <= b) {
        printf("%d %d %d\n", a, c, b);
    } else if (b <= a && a <= c) {
        printf("%d %d %d\n", b, a, c);
    } else if (b <= c && c <= a) {
        printf("%d %d %d\n", b, c, a);
    } else if (c <= a && a <= b) {
        printf("%d %d %d\n", c, a, b);
    } else {
        printf("%d %d %d\n", c, b, a);
    }

    return 0;
}