Lab 1

.gitignore

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+*
+!*.*
+!*/
+
+*.out
+.vscode/

README.md

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+# Peter's solutions for CITS2002 labs

Week 2/README.md

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+# Week 2
+
+Lab sheet:
+http://web.archive.org/web/20210731041540/http://teaching.csse.uwa.edu.au/units/CITS2002/labsheets/labsheet1.php

Week 2/refresher_tasks/1_coins.c

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+
+/*
+* 1 [integer arithmetic, basic loop] When Australia first adopted decimal
+* currency in 1966, coins had the denominations of 1c, 2c, 5c, 10c, 20c, and
+* (a round!) 50c. If a person purchased something valued at $1 or less, and paid
+* with a $1 note (yes), write a program to list the minimum number of coins, and
+* their demoninations, that they should receive as change.
+*/
+
+#include <stdlib.h>
+#include <stdio.h>
+
+/*
+* argument => cost in cents.
+* Assume a value of less than 100c as per the question.
+* Assume only the first argument has a price, else use the default example price
+*/
+int main(int argc, char const *argv[])
+{
+    int price = 53;
+    if (argc > 1)
+    {
+        price = 0;
+        int i = 0;
+        while (argv[1][i] != '\0')
+        {
+            int digit = argv[1][i]-'0';
+            if (digit > 9 || digit < 0) 
+            {
+                exit(EXIT_FAILURE);
+            }
+            price *= 10;
+            price += digit;
+            i++;
+        }
+    }
+    int remainder = 100 - price;
+    const int coinValues[] = {50, 20, 10, 5, 2, 1};
+    printf("Change: ");
+    for (size_t i = 0; i < 6; i++)
+    {
+        int coinValue = coinValues[i];
+        if (remainder / coinValue > 0) {
+            printf("%d %dc coins, ", remainder/coinValue, coinValue);
+            remainder -= coinValue*(remainder/coinValue);
+        }
+    }
+    printf("\n");
+    exit(EXIT_SUCCESS);
+}

Week 2/refresher_tasks/2_external_function.c

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+/*
+* 2 [calling external function] Using your chosen programming language, write a
+* short program to print out today's date and time
+* (example output: Thu Jul 29 18:19:34 2021). The actual format is unimportant.
+*/
+
+// man strftime
+
+#include <time.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+int main(void)
+{
+    char outstr[200];
+    time_t t;
+    struct tm *tmp;
+
+    t = time(NULL);
+    tmp = localtime(&t);
+    if (tmp == NULL) {
+        exit(EXIT_FAILURE);
+    }
+    strftime(outstr, sizeof(outstr), "%FT%T", tmp);
+    printf("%s\n", outstr);
+    exit(EXIT_SUCCESS);
+}

Week 2/refresher_tasks/3_floatingpoint.c

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+/*
+* 3 [floating-point numbers] In Lecture-2 we saw how some (in fact, most)
+* floating-point values cannot be represented exactly on contemporary computers
+* and, so, we must use them with great caution, or not at all. In your chosen
+* programming language, repeat the exercise from Lecture-2, displaying
+* sufficient decimal-points to 'expose' the problem.
+*/
+
+#include <stdio.h>
+
+int main(void)
+{
+    float f = 1024.533;
+    printf("%.25f\n",f);
+    // Answer is 1024.5329589843750000000000000 due to imprecision.
+    return 0;
+}

Week 2/refresher_tasks/4_1d_array.c

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+/*
+* 4 [integer arithmetic, 1D array] Revise (or learn) how to generate a 
+* non-negative random integer in your chosen programming language. Saturday 
+* Lotto involves drawing 6 unique numbers, between 1 and 45. Write a simple 
+* program to choose and display your 6 lucky numbers.
+*/
+
+#include <time.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+#define NUMBERS 6
+#define LOWER 1
+#define UPPER 45
+#define RANGE UPPER-LOWER+1
+
+
+int main(void)
+{
+    srand(time(NULL)); // Seed rng
+    int luckyNumbers[NUMBERS];
+    for (size_t i = 0; i < NUMBERS; i++)
+    {
+        luckyNumbers[i] = rand() % RANGE + LOWER;
+    }
+
+    // Could've printf in the last loop but seems like the exercise wants 
+    // a 1D array.
+
+    printf("Lucky numbers ");
+    for (size_t i = 0; i < NUMBERS; i++)
+    {
+        printf("%d ",luckyNumbers[i]);
+    }
+    printf("\n");
+    
+    return 0;
+}
+

Week 2/refresher_tasks/5_2d_array.c

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+/*
+* 🌶 [2D array, nested loop] Fill a 2D array of, say, 10x20 integers with
+* non-negative random integers. Without using your language's builtin/standard
+* sort() method/function, print out the second largest value in the array.
+*/
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+
+
+#define X_LENGTH 10
+#define Y_LENGTH 20
+
+// Testing
+void iterArray(int arr[][Y_LENGTH]) {
+    int n = 0;
+    for (int i = 0; i < X_LENGTH; i++)
+    {
+        for (int j = 0; j < Y_LENGTH; j++)
+        {
+            arr[i][j] = n;
+            n++;
+        }
+    }
+}
+
+void randomizeArray(int arr[][Y_LENGTH]) {
+    srand(time(NULL)); // Seed rng
+    for (int i = 0; i < X_LENGTH; i++)
+    {
+        for (int j = 0; j < Y_LENGTH; j++)
+        {
+            arr[i][j] = rand();
+        }
+    }
+}
+
+int twoLargest(int arr[][Y_LENGTH]) {
+    int secondLargest = 0;
+    int largest = 0;
+    for (int i = 0; i < X_LENGTH; i++)
+    {
+        for (int j = 0; j < Y_LENGTH; j++)
+        {
+            if (arr[i][j] > largest)
+            {
+                secondLargest = largest;
+                largest = arr[i][j];
+            }
+        } 
+    }
+    return secondLargest;
+}
+
+int main(void)
+{
+    int arr[X_LENGTH][Y_LENGTH];
+    // randomizeArray(arr);
+    iterArray(arr);
+    printf("Second largest : %d\n", twoLargest(arr));
+    return 0;
+}
+
+

Week 2/rot13/rotate.c

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+#include <stdio.h>   // => printf()
+#include <stdlib.h>  // => exit(), EXIT_SUCCESS, EXIT_FAILURE
+#include <string.h>  // strlen()
+#include <ctype.h>   // isupper(), islower()
+
+#include <unistd.h>
+
+// Compile this program with:
+//    cc -std=c11 -Wall -Werror -o rotate rotate.c
+
+//  The rotate function returns the character ROT positions further along the
+//  alphabetic character sequence from c, or c if c is not lower-case
+
+char rotate(char c, int rot)
+{
+    // Check if c is lower-case or not
+    if(islower(c)) {
+        // The ciphered character is ROT positions beyond c,
+        // allowing for wrap-around
+        return ('a' + (c - 'a' + rot) % 26);
+    } else if (isupper(c))
+        return ('A' + (c - 'A' + rot) % 26);
+    else {
+        return c;
+    }
+}
+
+void rotateString(char string[], int rot) {
+    // Define a variable for a later loop
+    int i;
+    // Calculate the length of the first argument
+    int length = strlen(string);
+
+    // Loop for every character in the text
+    for(i = 0; i < length; i++) {
+        // Determine and print the ciphered character
+        char c = string[i];
+        printf("%d :\t%c => %c\n", i, c, rotate(c, rot));
+    }
+
+    // Print one final new-line character
+    printf("\n");
+}
+
+//  Execution of the whole program begins at the main function
+
+int main(int argcount, char *argvalue[])
+{
+    int rot = 13;
+    for (int i = 1; i < argcount; i++)
+    {
+        char *ptr;
+        int n = (int)strtol(argvalue[i], &ptr, 10);
+        if (*ptr == '\0') {
+            rot = n;
+            printf("Rotate by %d\n\n", rot);
+        } else {
+            // Try reading file
+            if (access(argvalue[i], F_OK) == 0)
+            {
+                printf("-- Open file %s --\n\n", argvalue[i]);
+                FILE* f = fopen(argvalue[i], "r");
+                char c;
+                while ((c = getc(f)) != EOF)
+                {
+                    putchar(rotate(c, rot));
+                }
+                fclose(f);
+            }
+            
+            // Else interpret as string
+            printf("-- String %d --\n\n",i);
+            rotateString(argvalue[i], rot);
+            printf("-- End of string %d --\n\n",i);
+        }
+
+    }
+    
+    // Exit indicating success
+    exit(EXIT_SUCCESS);
+    return 0;
+}