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12.20 Lab10

introduction-to-computer-science-laboratory-10.pdf

Sequences can have same element and have the order

  1. Finish the exercises present in the tutorial.

  2. Identify the issues in the following C programs. Then fix the programs, avoiding the use of global variables while maintaining the original intended functionality:

    A.

    #include <stdio.h>
int n;
int i;
int prime = 1;
void isPrime() {
    i = 2;
    while(i < n && prime) 
        if(n % 1 == 0) {
            prime = 0;
        }
        i++;
    }
}
int main() {
    scanf("%d", &n);
    isPrime();
    if(prime) {
        printf("The number %d is prime\n", n);
    } 
    else {
        printf("The number %d is not prime\n", n);
    }
    return 0;
}

    Corrected:

    #include <stdio.h>

int isPrime(int n) {
    int i = 2;
    int prime = 1;
    if(n <= 1) {
        prime = 0;
        return prime;
    }
    else if(n == 2) {
        prime = 1;
        return prime;
    }
    while(i < n && prime) {
        if(n % i == 0) {
            prime = 0;
            return prime;
        }
        i++;
    }
    return prime;
}

int main() {
    int n;
    scanf("%d", &n);
    int prime = isPrime(n);
    if(prime) {
        printf("The number %d is prime\n", n);
    } 
    else {
        printf("The number %d is not prime\n", n);
    }
    return 0;
}

    B.

    #include <stdio.h>
#define MAX_SIZE 100
int evens;
int odds;
int arr[MAX_SIZE];
int size;
int result;
int i;
int n;
void isEven() {
    if(n % 2 == 0) {
        result = 1;
    } else {
        result = 0;
    }
}
void moreEvens() {
    for (i = 0; i < size; i++) {
        n = arr[i];
        isEven();
        if(result == 1) {
            evens++;
        } else {
            odds++;
        }
    }
    result = evens > odds;
}
int main() {
    scanf("%d", &size);
    for(i = 0; i < size; i++)
        scanf("%d", &arr[i]);
    i = 0;
    evens = 0;
    odds = 0;
    moreEvens();
    if(result) {
        printf("There is more evens than odds\n");
    } else {
        printf("There is more or equal odds than evens\n");
    }
    return 0;
}

    Corrected:

    #include <stdio.h>
#define MAX_SIZE 100

int isEven(int n, int result) {
    if (n % 2 == 0) {
        result = 1;
        return result;
    }
    else {
        result = 0;
        return result;
    }
}

int moreEvens(int size, int result,int arr[]) {
    int evens = 0;
    int odds = 0;
    for (int i = 0; i < size; i++) {
        int n = arr[i];
        result = isEven(n, result);
        if (result == 1) 
            evens++;
        else
            odds++;
    }
    result = (evens > odds);
    return result;
}

int main() {
    int size;
    int result;
    int arr[MAX_SIZE];
    scanf("%d", &size);
    for (int i = 0; i < size; i++)
        scanf("%d", &arr[i]);
    result = moreEvens(size, result, arr);
    if (result)
        printf("There is more evens than odds\n");
    else
        printf("There is more or equal odds than evens\n");
    return 0;
}

  3. For the following C functions over arrays, add the const​ modifier where it is needed.

    A.

    void loadArray(int a[], int size) {
    for(int i = 0; i < size; i++) {
        a[i] = i;
    }
}

    No need to add const​

    B.

    void copy(int a[], int b[], int size) {
    for(int i = 0; i < size; i++) {
        b[i] = a[i];
    }
}

    Corrected

    void copy(const int a[], int b[], int size) {
    for(int i = 0; i < size; i++) {
        b[i] = a[i];
    }
}

    C.

    void powArray(int a[], int size) {
    for(int i = 0; i < size; i++) {
        a[i] = a[i] * a[i];
    }
}

    No need

    D.

    void sumArrays(int a[], int b[], int c[], int size) {
    for(int i = 0; i < size; i++) {
        c[i] = a[i] + b[i];
    }
}

    Corrected:

    void sumArrays(const int a[],const int b[], int c[], int size) {
    for(int i = 0; i < size; i++) {
        c[i] = a[i] + b[i];
    }
}

  4. Implement a C function that, given 2 strings, determines if they are equal or not. Then write a main function that takes 2 strings from standard input and calls the previously defined function.

    #include <stdio.h>

int isEqual(char str1[], char str2[]) {
    for(int i = 0; str1[i] != '\0' || str2[i] != '\0'; i++) {
        if(str1[i] != str2[i]) 
            return 0;
    }
    return 1;
}


int main() {
    char str1[1000];
    char str2[1000];
    fgets(str1, 1000, stdin);
    fgets(str2, 1000, stdin);
    if(isEqual(str1, str2))
        printf("Yes, they are equal!");
    else
        printf("No, they are not euqal!");
}

  5. Design a function that, given a string, calculates its length. Write a main function that takes as input a string from the command line and calculates the string’s length.

    #include <stdio.h>

int length(char str[]) {
    int i;
    for(i = 0; str[i] != '\0'; i++) {}
    return i - 1;
}

int main() {
    char str[1000];
    fgets(str, 1000, stdin);
    int len = length(str);
    printf("%d", len);
}

  6. Write a function that, given a string s​, calculates the reverse of s​ and stores it in the same string. This function cannot use additional arrays. Afterward, write a main function that takes a string from standard input, prints it, and prints the reverse of the input.

    #include <stdio.h>

int length(char str[]) {
    int i;
    for(i = 0; str[i] != '\0'; i++) {}
    return i - 1;
}

void reverse(char str[]) {
    char temp;
    for(int i = 0; i < length(str) - i - 1; i++) {
        temp = str[length(str) - i - 1];
        str[length(str) - i - 1] = str[i];
        str[i] = temp;
    }
}

int main() {
    char str[1000];
    fgets(str, 1000, stdin);
    reverse(str);
    printf("%s", str);
}

  7. Write a C function that calculates the power of 2 using an array. This array must have a length of (n + 1)​ for every n​. Then write a main function that takes n​ as input from the command line and calculates the power of 2.

    #include<stdio.h>
#include<stdlib.h> 

void initial(int str[], int size) {
    for(int i = 0; i < size; i++) {
        str[i] = 2;
    }
}

int powt(int str[], int size) {
    int result = 1;
    for(int i = 0; i < size; i++) {
        result *= str[i];
    }
    return result;
}

int main(int argc, char *argv[]) {
    int size = atoi(argv[1]);
    int str[size];
    initial(str, size);
    printf("%d", powt(str, size));
}

Insert sort

#include <stdio.h>
#include <assert.h>
#define FALSE 0
#define TRUE 1
/* inserts the element at position index into
  Its sorted position in the sorted subarray
  Seq[0 .. index - 1].
  Precondition: index is a valid position of the array
  The subarray seq[0..index-1] is sorted.
 */
void sorted_insert(int seq[], int index) {
    assert (index >= 0);
    if (index > 0 && seq[index] < seq[index - 1]) {
        int aux = seq[index];
        seq[index] = seq[index - 1];
        seq[index - 1] = aux;
        sorted_insert(seq, index - 1);
    }
}
/* prints array contents from position lower to 
   Position upper - 1 */
void print_array(int seq[], int lower, int upper) {
    printf("{");
    for (int i = lower; i < upper - 1; i++) {
        printf("%d, ", seq[i]);
    }
    printf("%d}\n", seq[upper - 1]);
}
/* Sorts an array seq.
 * Precondition: size is >= 0, and is the size
 * of the array. 
 */
void sort(int seq[], int size) {
    if(size > 1) {
        sort(seq, size - 1);
        sorted_insert(seq, size - 1);
    }
/*     for (int i = 1; i < size; i++) {
        sorted_insert(seq, i);
    } */
}
int main() {
    int seq[11] = {1, 2, 33, 4, 5, 3, 6, 7, 8, 59, 25};
    print_array(seq, 0, 11);
    sort(seq, 11);
    print_array(seq, 0, 11);
    return 0;
}

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