Data Structures - Arrays - Traversal

In this tutorial we will learn to traverse an Array data structure in forward and reverse order.

Table of Content

• Tranversal
• Forward traversal
• Reverse traversal

Tranversal

To traverse an array means to access each of the element stored in the array. We can traverse an array in forward-direction (first element to last element) from left to right and in reverse-direction (last element to first element) from right to left.

Forward traversal

In the following C++ code we are traversing the array from left to right i.e., from the first element to the last element. The array in this example has size 5.

#include<iostream>
using namespace std;

const int MAX = 5;

int main(void) {
  int arr[MAX] = {1, 10, 5, 6, 3};
  int i;
  for (i = 0; i < MAX; i++) {
    cout << "arr[" << i << "] = " << arr[i] << endl;
  }
  return 0;
}

Output

arr[0] = 1
arr[1] = 10
arr[2] = 5
arr[3] = 6
arr[4] = 3

Time complexity of forward traversal is O(n).

Reverse traversal

In the following C++ code we are traversing the array in reverse order i.e., from the last element to the first element. The array in this example also has size 5.

#include<iostream>
using namespace std;

const int MAX = 5;

int main(void) {
  int arr[MAX] = {1, 10, 5, 6, 3};
  int i;
  for (i = MAX-1; i >= 0; i--) {
    cout << "arr[" << i << "] = " << arr[i] << endl;
  }
  return 0;
}

Output

arr[4] = 3
arr[3] = 6
arr[2] = 5
arr[1] = 10
arr[0] = 1

Time complexity of reverse traversal is O(n).