🟡 Intermediate · Lesson 20

1D Arrays

What is an Array?

An array is a collection of elements of the same data type stored in contiguous memory locations. Instead of declaring 10 separate integer variables, you can use one array of size 10.

Without Array vs With Array

// Without array (bad): 5 separate variables
int m1, m2, m3, m4, m5;

// With array (good): one declaration
int marks[5];  // Array of 5 integers

Key properties:

All elements are of the same type
Elements stored in contiguous memory
Each element accessed using its index (starting from 0!)
Size is fixed at declaration (in C89/C90)

💡 Memory Layout

For int marks[5], if the array starts at address 1000:
marks[0]=1000, marks[1]=1004, marks[2]=1008, marks[3]=1012, marks[4]=1016
(Each int = 4 bytes, so addresses differ by 4)

Declaration and Initialization

C Language

// Method 1: Declare only (garbage values)
int arr[5];

// Method 2: Declare and initialize
int marks[5] = {90, 85, 78, 92, 88};

// Method 3: Partial init (rest become 0)
int nums[5] = {10, 20};  // {10, 20, 0, 0, 0}

// Method 4: Size auto-detected from values
int primes[] = {2, 3, 5, 7, 11};  // Size = 5

// Method 5: Initialize all to zero
int zeros[10] = {0};  // All elements = 0

// Other types
float temps[7] = {36.5f, 37.0f, 36.8f};
char  grades[5] = {'A', 'B', 'A', 'C', 'B'};

Accessing Array Elements

Use the index inside square brackets. Index starts at 0, ends at size-1.

C Language

int marks[5] = {90, 85, 78, 92, 88};

printf("%d\\n", marks[0]);  // 90 (first element)
printf("%d\\n", marks[4]);  // 88 (last element, index = size-1)

marks[2] = 95;             // Change element at index 2
printf("%d\\n", marks[2]);  // Now prints 95

⚠️ Index Out of Bounds

Accessing arr[5] when size is 5 is undefined behavior — it may crash, produce wrong output, or corrupt memory. C does NOT check bounds automatically! Always stay within 0 to size-1.

Array Input and Output

C Language – Input N elements and print

#include <stdio.h>
int main() {
    int n;
    printf("How many elements? ");
    scanf("%d", &n);

    int arr[n];

    // Input
    printf("Enter %d numbers:\\n", n);
    for (int i = 0; i < n; i++) {
        printf("arr[%d] = ", i);
        scanf("%d", &arr[i]);
    }

    // Output
    printf("Array: ");
    for (int i = 0; i < n; i++) {
        printf("%d ", arr[i]);
    }
    printf("\\n");
    return 0;
}

How many elements? 5 Enter 5 numbers: arr[0] = 10 arr[1] = 25 arr[2] = 8 arr[3] = 40 arr[4] = 15 Array: 10 25 8 40 15

Array Operations

Finding Sum, Average, Max, Min

C Language – Complete Array Stats

#include <stdio.h>
int main() {
    int marks[] = {85, 92, 78, 96, 70};
    int n = sizeof(marks) / sizeof(marks[0]);  // Auto calculate size

    int sum = 0, max = marks[0], min = marks[0];

    for (int i = 0; i < n; i++) {
        sum += marks[i];
        if (marks[i] > max) max = marks[i];
        if (marks[i] < min) min = marks[i];
    }

    printf("Sum     = %d\\n", sum);
    printf("Average = %.2f\\n", (float)sum / n);
    printf("Maximum = %d\\n", max);
    printf("Minimum = %d\\n", min);
    return 0;
}

Sum = 421 Average = 84.20 Maximum = 96 Minimum = 70

Linear Search

C Language – Linear Search

#include <stdio.h>
int main() {
    int arr[] = {10, 25, 8, 40, 15};
    int n = 5, key, found = 0;
    printf("Search for: ");
    scanf("%d", &key);

    for (int i = 0; i < n; i++) {
        if (arr[i] == key) {
            printf("Found at index %d\\n", i);
            found = 1;
            break;
        }
    }
    if (!found) printf("Not found\\n");
    return 0;
}

Bubble Sort

C Language – Bubble Sort

#include <stdio.h>
int main() {
    int arr[] = {64, 34, 25, 12, 22};
    int n = 5;

    for (int i = 0; i < n-1; i++) {
        for (int j = 0; j < n-i-1; j++) {
            if (arr[j] > arr[j+1]) {
                int temp = arr[j];
                arr[j] = arr[j+1];
                arr[j+1] = temp;
            }
        }
    }
    printf("Sorted: ");
    for (int i = 0; i < n; i++) printf("%d ", arr[i]);
    return 0;
}

Sorted: 12 22 25 34 64

Summary

Array = collection of same-type elements in contiguous memory
Index starts at 0, ends at size - 1
Declaration: type name[size];
Use sizeof(arr)/sizeof(arr[0]) to get array length
Always stay within bounds — C doesn't check automatically!
Use for loops to traverse, search, sort arrays

Array क्या है?

Array same data type के elements का collection है जो contiguous memory locations में store होते हैं। 10 अलग integer variables declare करने की बजाय, size 10 का एक array use करें।

💡 Memory Layout

int marks[5] के लिए: marks[0], marks[1], marks[2], marks[3], marks[4] — सभी एक साथ memory में। Index हमेशा 0 से शुरू होता है!

Declaration और Initialization

C Language

int marks[5];                           // Declare only
int marks[5] = {90, 85, 78, 92, 88};  // Declare + Initialize
int primes[] = {2, 3, 5, 7, 11};      // Size auto-detect
int zeros[10] = {0};                   // सब 0 initialize

Elements Access करना

C Language

int marks[] = {90, 85, 78, 92, 88};
printf("%d\\n", marks[0]);  // 90 — पहला element
printf("%d\\n", marks[4]);  // 88 — आखिरी element
marks[2] = 95;             // index 2 का value बदला

⚠️ Index Out of Bounds

Size 5 के array में arr[5] access करना undefined behavior है — program crash हो सकता है। C automatically bounds check नहीं करता! हमेशा 0 से size-1 के बीच रहें।

Array Input और Output

C Language

int n = 5, arr[5];
printf("5 numbers daalen:\\n");
for(int i=0; i<n; i++) scanf("%d", &arr[i]);  // Input
for(int i=0; i<n; i++) printf("%d ", arr[i]); // Output

Array Operations

Sum, Average, Max, Min

int marks[] = {85, 92, 78, 96, 70};
int n = sizeof(marks)/sizeof(marks[0]);
int sum=0, max=marks[0], min=marks[0];
for(int i=0; i<n; i++) {
    sum += marks[i];
    if(marks[i]>max) max=marks[i];
    if(marks[i]<min) min=marks[i];
}
printf("Sum=%.d Avg=%.2f Max=%d Min=%d\\n",sum,(float)sum/n,max,min);

Sum=421 Avg=84.20 Max=96 Min=70

सारांश

Array = same type के elements का contiguous memory में collection
Index 0 से शुरू होता है, size - 1 पर खत्म
Declaration: type name[size];
Array length: sizeof(arr)/sizeof(arr[0])
C automatically bounds check नहीं करता — सावधान रहें!
Traverse, search, sort के लिए for loops use करें

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