Week 1: Structures, Arrays, Strings, and Word Frequency

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Q1. Student Marks Using Structure

Objective: Store details of n students, calculate average marks, and display students scoring above 75%.

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

struct Student {
    int roll_no;
    char name[50];
    float marks[5];
};

int main() {
    int n;
    printf("Enter number of students: ");
    scanf("%d", &n);

    struct Student students[n];

    // Input student details
    for (int i = 0; i < n; i++) {
        printf("Enter details for Student %d:\n", i + 1);
        printf("Roll No: ");
        scanf("%d", &students[i].roll_no);

        printf("Name: ");
        scanf("%s", students[i].name);

        printf("Marks: ");
        for (int j = 0; j < 5; j++) {
            scanf("%f", &students[i].marks[j]);
        }
    }

    // Display students with average > 75
    printf("\nStudents scoring above 75%%:\n");
    for (int i = 0; i < n; i++) {
        float total = 0;
        for (int j = 0; j < 5; j++)
            total += students[i].marks[j];

        float average = total / 5;
        if (average > 75.0) {
            printf("Roll No: %d, Name: %s, Average Marks: %.2f\n", 
                    students[i].roll_no, students[i].name, average);
        }
    }

    return 0;
}

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Q2. Remove Duplicates from Array

Objective: Input n elements in an array and remove duplicates.

#include <stdio.h>

int main() {
    int n, i, j, k;
    printf("Enter number of elements: ");
    scanf("%d", &n);

    int arr[n];
    printf("Enter elements: ");
    for(i = 0; i < n; i++) scanf("%d", &arr[i]);

    // Remove duplicates
    for(i = 0; i < n; i++) {
        for(j = i + 1; j < n; ) {
            if(arr[i] == arr[j]) {
                for(k = j; k < n - 1; k++) arr[k] = arr[k + 1];
                n--;
            } else j++;
        }
    }

    printf("Array after removing duplicates: ");
    for(i = 0; i < n; i++) printf("%d ", arr[i]);
    printf("\n");

    return 0;
}

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Q3. Patient Records Using Structure

Objective: Store patient details including admission date and search patients by month & year.

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

#define MAX_PATIENTS 100
#define MAX_NAME_LEN 100

struct Date {
    int day;
    int month;
    int year;
};

struct Patient {
    int id;
    char name[MAX_NAME_LEN];
    char disease[MAX_NAME_LEN];
    struct Date admissionDate;
};

int main() {
    struct Patient patients[MAX_PATIENTS];
    int n, i, searchMonth, searchYear;

    printf("Enter number of patients: ");
    scanf("%d", &n);

    for(i = 0; i < n; i++) {
        printf("Patient %d:\n", i + 1);
        printf("ID: "); scanf("%d", &patients[i].id);
        getchar(); // Consume leftover newline
        printf("Name: "); fgets(patients[i].name, MAX_NAME_LEN, stdin);
        patients[i].name[strcspn(patients[i].name, "\n")] = '\0';
        printf("Disease: "); fgets(patients[i].disease, MAX_NAME_LEN, stdin);
        patients[i].disease[strcspn(patients[i].disease, "\n")] = '\0';
        printf("Admission Date (dd mm yyyy): ");
        scanf("%d %d %d", &patients[i].admissionDate.day, 
                          &patients[i].admissionDate.month, 
                          &patients[i].admissionDate.year);
    }

    printf("Enter month and year to search: ");
    scanf("%d %d", &searchMonth, &searchYear);

    int found = 0;
    printf("Patients admitted in %02d/%d:\n", searchMonth, searchYear);
    for(i = 0; i < n; i++) {
        if(patients[i].admissionDate.month == searchMonth &&
           patients[i].admissionDate.year == searchYear) {
            printf("ID: %d, Name: %s, Disease: %s, Date: %02d-%02d-%04d\n",
                   patients[i].id, patients[i].name, patients[i].disease,
                   patients[i].admissionDate.day, patients[i].admissionDate.month,
                   patients[i].admissionDate.year);
            found = 1;
        }
    }

    if(!found) printf("No patients admitted in %02d/%d\n", searchMonth, searchYear);

    return 0;
}

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Q4. Word Frequency in Paragraph

Objective: Count frequency of each word in a paragraph.

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

#define MAX_WORDS 100
#define MAX_LENGTH 1000

int main() {
    char paragraph[MAX_LENGTH];
    char words[MAX_WORDS][50];
    int count[MAX_WORDS] = {0};
    int i, wordCount = 0;

    printf("Enter paragraph:\n");
    fgets(paragraph, MAX_LENGTH, stdin);

    // Convert to lowercase and remove punctuation
    for(i = 0; paragraph[i]; i++) {
        if (isalpha(paragraph[i]) || isspace(paragraph[i]))
            paragraph[i] = tolower(paragraph[i]);
        else
            paragraph[i] = ' ';
    }

    // Split into words
    char *word = strtok(paragraph, " ");
    while(word != NULL) {
        int found = 0;
        for(i = 0; i < wordCount; i++) {
            if(strcmp(words[i], word) == 0) {
                count[i]++;
                found = 1;
                break;
            }
        }
        if(!found) {
            strcpy(words[wordCount], word);
            count[wordCount] = 1;
            wordCount++;
        }
        word = strtok(NULL, " ");
    }

    // Print result
    printf("\nWord Frequencies:\n");
    for(i = 0; i < wordCount; i++)
        printf("%s - %d\n", words[i], count[i]);

    return 0;
}

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Key Points for Week 1:

1. Structures help organize related data (Student, Patient, Date).
2. Arrays can be used to store multiple values; removing duplicates requires shifting elements.
3. Strings can be manipulated using fgets, strtok, strcmp, and strcpy.
4. Word frequency counting involves converting text to lowercase, removing punctuation, and tracking occurrences.

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