Array Traversal and Operations
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Traversal
Traversal means visiting every element of an array exactly once, almost always with a for loop that walks from index 0 to size−1. It's the foundation nearly every other array operation is built on top of.
Example: Traversal
#include <iostream>
using namespace std;
int main() {
int arr[] = {3, 6, 9, 12};
for (int i = 0; i < 4; i++) cout << arr[i] << " "; // visit each element once
cout << endl;
return 0;
}public class Main {
public static void main(String[] args) {
int[] arr = {3, 6, 9, 12};
for (int i = 0; i < arr.length; i++) System.out.print(arr[i] + " ");
System.out.println();
}
}arr = [3, 6, 9, 12]
for x in arr:
print(x, end=" ")
print()#include <stdio.h>
int main() {
int arr[] = {3, 6, 9, 12};
for (int i = 0; i < 4; i++) printf("%d ", arr[i]);
printf("\n");
return 0;
}Login to try C/C++/Java code in the editor
Searching
Linear search traverses the array and compares each element to a target value, stopping early if it finds a match. It's simple and works on unsorted data, though it takes O(n) time in the worst case since it may have to check every element.
Example: Searching
#include <iostream>
using namespace std;
int main() {
int arr[] = {9, 4, 7, 2, 5};
int target = 7, foundAt = -1;
for (int i = 0; i < 5; i++) {
if (arr[i] == target) { foundAt = i; break; } // stop early on match
}
cout << "Found at index: " << foundAt << endl;
return 0;
}public class Main {
public static void main(String[] args) {
int[] arr = {9, 4, 7, 2, 5};
int target = 7, foundAt = -1;
for (int i = 0; i < arr.length; i++) {
if (arr[i] == target) { foundAt = i; break; }
}
System.out.println("Found at index: " + foundAt);
}
}arr = [9, 4, 7, 2, 5]
target = 7
found_at = arr.index(target) if target in arr else -1
print("Found at index:", found_at)#include <stdio.h>
int main() {
int arr[] = {9, 4, 7, 2, 5};
int target = 7, foundAt = -1;
for (int i = 0; i < 5; i++) {
if (arr[i] == target) { foundAt = i; break; }
}
printf("Found at index: %d\n", foundAt);
return 0;
}Login to try C/C++/Java code in the editor
Insertion and Deletion
Because a fixed-size array stores elements contiguously, inserting or deleting in the middle means physically shifting every element after that position over by one slot, which is an O(n) operation, unlike a linked list where the same change is O(1) once you're at the right node.
Example: Insertion and Deletion
#include <iostream>
using namespace std;
int main() {
int arr[6] = {1, 2, 4, 5, 0, 0};
int n = 4;
// Insert 3 at index 2: shift everything after it right by one.
for (int i = n; i > 2; i--) arr[i] = arr[i - 1];
arr[2] = 3;
n++;
for (int i = 0; i < n; i++) cout << arr[i] << " ";
cout << endl;
return 0;
}public class Main {
public static void main(String[] args) {
int[] arr = {1, 2, 4, 5, 0, 0};
int n = 4;
for (int i = n; i > 2; i--) arr[i] = arr[i - 1];
arr[2] = 3;
n++;
for (int i = 0; i < n; i++) System.out.print(arr[i] + " ");
System.out.println();
}
}arr = [1, 2, 4, 5]
arr.insert(2, 3) # shifting every later element right by one, O(n)
print(*arr)#include <stdio.h>
int main() {
int arr[6] = {1, 2, 4, 5, 0, 0};
int n = 4;
for (int i = n; i > 2; i--) arr[i] = arr[i - 1];
arr[2] = 3;
n++;
for (int i = 0; i < n; i++) printf("%d ", arr[i]);
printf("\n");
return 0;
}Login to try C/C++/Java code in the editor
Counting and Frequency
Counting how many times a value appears, or building a full frequency count of every distinct value, is a traversal that keeps a running tally as it scans, often using a separate array or hash map indexed by value.
Example: Counting and Frequency
#include <iostream>
using namespace std;
int main() {
int arr[] = {1, 2, 2, 3, 2, 1};
int target = 2, count = 0;
for (int i = 0; i < 6; i++)
if (arr[i] == target) count++;
cout << "Count of " << target << ": " << count << endl;
return 0;
}public class Main {
public static void main(String[] args) {
int[] arr = {1, 2, 2, 3, 2, 1};
int target = 2, count = 0;
for (int x : arr) if (x == target) count++;
System.out.println("Count of " + target + ": " + count);
}
}arr = [1, 2, 2, 3, 2, 1]
target = 2
count = arr.count(target)
print(f"Count of {target}:", count)#include <stdio.h>
int main() {
int arr[] = {1, 2, 2, 3, 2, 1};
int target = 2, count = 0;
for (int i = 0; i < 6; i++)
if (arr[i] == target) count++;
printf("Count of %d: %d\n", target, count);
return 0;
}Login to try C/C++/Java code in the editor
Useful Array Operations
Practicing sum, average, and reversal on arrays builds real intuition for index arithmetic and loop boundaries. These simple operations are also the building blocks for more advanced array techniques like two-pointer and sliding-window algorithms.
Example: Useful Array Operations
#include <iostream>
using namespace std;
int main() {
int arr[] = {4, 8, 15, 16, 23};
int n = 5, sum = 0;
for (int i = 0; i < n; i++) sum += arr[i];
double avg = (double)sum / n;
for (int i = 0; i < n / 2; i++) swap(arr[i], arr[n - 1 - i]); // reversal
cout << "Sum: " << sum << ", Avg: " << avg << ", arr[0] after reverse: " << arr[0] << endl;
return 0;
}public class Main {
public static void main(String[] args) {
int[] arr = {4, 8, 15, 16, 23};
int n = arr.length, sum = 0;
for (int x : arr) sum += x;
double avg = (double) sum / n;
for (int i = 0; i < n / 2; i++) {
int tmp = arr[i]; arr[i] = arr[n - 1 - i]; arr[n - 1 - i] = tmp;
}
System.out.println("Sum: " + sum + ", Avg: " + avg + ", arr[0] after reverse: " + arr[0]);
}
}arr = [4, 8, 15, 16, 23]
total = sum(arr)
avg = total / len(arr)
arr.reverse()
print("Sum:", total, ", Avg:", avg, ", arr[0] after reverse:", arr[0])#include <stdio.h>
int main() {
int arr[] = {4, 8, 15, 16, 23};
int n = 5, sum = 0;
for (int i = 0; i < n; i++) sum += arr[i];
double avg = (double)sum / n;
for (int i = 0; i < n / 2; i++) {
int tmp = arr[i]; arr[i] = arr[n - 1 - i]; arr[n - 1 - i] = tmp;
}
printf("Sum: %d, Avg: %.1f, arr[0] after reverse: %d\n", sum, avg, arr[0]);
return 0;
}Login to try C/C++/Java code in the editor
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