gistfile1.txt

//
//  main.c
//  guavajuice
//
//  Created by Aaron Wojnowski on 2014-10-24.
//  Copyright (c) 2014 aaron. All rights reserved.
//

#include <stdio.h>
#include <string.h>

#pragma mark - Declarations

void pointerArithmetic();

void question1();
void question2to4();
void question5();
void question6();
void question7();
void question8to10();

void questionLong1();
void questionLong2();

#pragma mark - Main

int main(int argc, const char * argv[]) {
    
    printf("GORD 2060\n");
    printf("=========\n\n");
    
    // pointer arithmetic
    
    pointerArithmetic();
    
    // midterm preparation questions
    
    question1();
    question2to4();
    question5();
    question6();
    question7();
    question8to10();
    
    questionLong1();
    questionLong2();
    
    return 0;
    
}

#pragma mark - Helper Methods

void printIntArray(int *array, int size) {
    
    printf("[");
    {
        for (int i = 0; i < size; i++) {
            
            printf("%d",array[i]);
            if (i + 1 < size) printf(", ");
            
        }
    }
    printf("]\n");
    
}

#pragma mark - Pointer Arithmetic

void pointerArithmetic() {
    
    printf("Pointer Arithmetic\n");
    printf("------------------\n\n");
    
    // let's do some looking to arrays and
    // how to interact with elements
    
    int const arraySize = 10;
    int array[arraySize];
    for (int i = 0; i < arraySize; ++i) {
        
        int const value = i + 1;
        
        // all arrays in c are just pointers to the starting memory
        // array[1] doesn't actually go to the "first element" it just
        // takes the starting pointer and increments it by 1
        // however, it is assignable which is nice
        
        // here, we could do array[i] = value;
        // or we could manipulate the pointer without subscripting
        
        // here we use memcpy since that allows us to write to the memory directly
        memcpy(array + i, &value, sizeof(value));
        
        // this does the same thing too (copies memory into the pointer returned by array[i])
        memcpy(&array[i], &value, sizeof(value));
        
    }
    printIntArray(array, arraySize);
    
    printf("\n");
    
}

#pragma mark - Question Requirements

char *printit(char *s) {
    
    char *temp = s;
    
    // goes through temp and prints it out
    while (*temp) putchar(*temp++);
    
    // goes back through temp and prints it in reverse
    // initially, temp is pointing one byte higher than where the last character is stored
    // therefore it is ok to dereference the decremented "temp"
    do {
        
        putchar(*--temp);
        
    } while (temp - s);
    
    putchar('\n');
    return(temp);
    
}

#pragma mark - Questions

void question1() {
    
    printf("Question 1\n");
    printf("----------\n\n");
    
    int const ARRAY_SIZE = 5;
    
    int array[ARRAY_SIZE];
    for (int i = 0; i < sizeof(array) / sizeof(int); i++)
        array[i] = (i + 1) * 2;
    
    printf("Initial array: \n");
    printIntArray(array, ARRAY_SIZE);
    
    int *pi;
    for (pi = &array[0]; pi < &array[ARRAY_SIZE]; )
        *++pi = 0;
    
    printf("\n");
    printf("Array after iterating: \n");
    printIntArray(array, ARRAY_SIZE);
    
    printf("\n");
    
}

void question2to4() {
    
    printf("Questions 2 to 4\n");
    printf("----------------\n\n");
    
    printf("2: ");
    printit("oh-oh");
    
    printf("3: ");
    char *x = printit("oh-oh");
    printf("   x: %s\n",x);
    
    printf("4: *--temp dereferences the pointer after it is decremented whereas --*temp decrements the dereferenced pointer value.\n");
    
    printf("\n");
    
}

void question5() {
    
    printf("Question 5\n");
    printf("----------\n\n");
    
    // note: the code given in the question is incorrect (there is a semicolon where
    // there should be a comma)
    char *string, **strings;
    
    // fill strings variable
    char *temp = "test";
    strings = &temp;
    
    // initially string will point to strings just fine but then it's incremented
    // and I have no idea what the fuck happens then
    while ((string = *strings++) != NULL) {
        
        printf("%s\n",string);
        
    }
    
    printf("\n");
    
}

void question6() {
    
    printf("Question 6\n");
    printf("----------\n\n");
    
    int const ARRAY_SIZE = 5;
    int array[ARRAY_SIZE];
    for (int i = 0; i < sizeof(array) / sizeof(int); i++) {
        
        array[i] = (i + 1) * 2;
        //array[i] = 0;
        
    }
    
    int non_zero = 0;
    for (int i = 0; i < ARRAY_SIZE; i += 1)
        non_zero += array[i];
    
    if (!non_zero) {
        
        printf("Values are all zero.\n");
        
    } else {
        
        printf("Values are not all zero.\n");
        
    }
    
    printf("\n");
    
}

void question7() {
    
    printf("Question 7\n");
    printf("----------\n\n");
    
    int ints[20] = { 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200 };
    int *ip = ints + 3;
    
    printf("Initial array: \n");
    printIntArray(ints, 20);
    printf("\n");
    
    printf("ints:        %p\n",ints);
    printf("ints[4]:     %d\n",ints[4]);
    printf("*(ints + 4): %d\n",*(ints + 4));
    printf("*ints + 4:   %d\n",*ints + 4);
    printf("ip[-2]:      %d\n",ip[-2]);
    printf("&ip + 4:     memory location of the ip pointer + (4 * 4 bytes)\n");
    
    printf("\n");
    
}

void question8to10() {
    
    printf("Questions 8 to 10\n");
    printf("-----------------\n\n");
    
    struct inner {
        int x;
        double y;
        char *p;
    } c1 = {4, 1.7, "Happy Halloween"};
    
    struct outer {
        int x;
        struct inner str_in;
    } c2 = {2, c1};
    
    c2.str_in.p = "Happy New Year";
    printf("8:  %s\n",c2.str_in.p);
    
    struct inner *pointer = &c1;
    printf("9:  %s : %s\n",pointer->p,c1.p);
    printf("10: Question is duplicate of 9.\n");
    
    printf("\n");
    
}

void merge(int *array1, int *array2, int *array3) {
    
    int arrayIndex1 = 0;
    int arrayIndex2 = 0;
    int arrayIndex = 0;
    
    while (1) {
        
        int integer1 = array1[arrayIndex1];
        int integer2 = array2[arrayIndex2];
        
        // are we at the end?
        if (integer1 == -1 && integer2 == -1) return;
        
        // figure out which integer is greater and then add that
        if (integer1 == -1) array3[arrayIndex] = integer2, arrayIndex2 ++;
        else if (integer2 == -1) array3[arrayIndex] = integer1, arrayIndex1 ++;
        else if (integer1 < integer2) array3[arrayIndex] = integer1, arrayIndex1 ++;
        else array3[arrayIndex] = integer2, arrayIndex2 ++;
        
        arrayIndex ++;
        
    }
    
}

void questionLong1() {
    
    printf("Long Answer Question 1\n");
    printf("----------------------\n\n");
    
    int const arraySize = 11;
    int const mergedArraySize = arraySize * 2 - 2;
    
    int array[arraySize]  = { 20, 31, 50, 88, 105, 666, 889, 890, 901, 905, -1 };
    int array2[arraySize] = { 1, 4, 8, 25, 68, 101, 546, 700, 705, 980, -1 };
    int array3[mergedArraySize];
    merge(array, array2, array3);
    
    printf("Merged array:\n");
    printIntArray(array3, mergedArraySize);
    
    printf("\n");
    
}

// name changed since dup already exists in this namespace
// using the string.h module to get the length of the string
int aaron_dup(char *string) {
    
    int size = (int)strlen(string);
    if (size % 2 != 0) return 0;
    
    for (int i = size / 2; i < size; i++) {
        
        if (string[i - size / 2] != string[i]) return 0;
        
    }
    
    return 1;
    
}

void questionLong2() {
    
    printf("Long Answer Question 2\n");
    printf("----------------------\n\n");
    
    char *string;
    string = "giantsnake";
    //string = "redred";
    
    if (aaron_dup(string)) {
        
        printf("String \"%s\" is duplicated.\n",string);
        
    } else {
        
        printf("String \"%s\" is not duplicated.\n",string);
        
    }
    
    printf("\n");
    
}