determining whether a array is a subsequence of another array

To determine whether an array is a subsequence of another array in C++, you can follow these steps:

  1. Define two index variables, i and j, to keep track of the positions in the arrays.
  2. Start a loop that iterates over both arrays simultaneously. This loop will continue until either the subsequence array is fully traversed or the main array is fully traversed.
  3. Inside the loop, compare the elements at the current positions i and j in both arrays. If they are equal, increment both i and j to move to the next elements in both arrays.
  4. If the elements are not equal, only increment the j index to move to the next element in the main array.
  5. After the loop ends, check if the subsequence array is fully traversed. If it is, then it is a subsequence of the main array. Otherwise, it is not.
  6. Return the result of the check.

Here's an example implementation of this algorithm in C++:

#include <iostream>
#include <vector>

bool isSubsequence(const std::vector<int>& subsequence, const std::vector<int>& mainArray) {
    int i = 0, j = 0;
    while (i < subsequence.size() && j < mainArray.size()) {
        if (subsequence[i] == mainArray[j]) {
            i++;
            j++;
        } else {
            j++;
        }
    }
    return i == subsequence.size();
}

int main() {
    std::vector<int> subsequence = {2, 4, 6};
    std::vector<int> mainArray = {1, 2, 3, 4, 5, 6, 7};

    bool result = isSubsequence(subsequence, mainArray);
    std::cout << "Is subsequence? " << (result ? "Yes" : "No") << std::endl;

    return 0;
}

In this example, we have a isSubsequence function that takes two vectors as arguments: subsequence, which represents the subsequence array, and mainArray, which represents the main array. The function returns a boolean value indicating whether the subsequence is present in the main array.

The isSubsequence function uses the algorithm described above. It initializes the indices i and j to 0 and then iterates over both arrays. If the elements at the current indices are equal, both indices are incremented to move to the next elements. If the elements are not equal, only the j index is incremented.

After the loop ends, the function checks if the subsequence array is fully traversed (i.e., i is equal to the size of the subsequence array). If it is, the function returns true, indicating that the subsequence is present in the main array. Otherwise, it returns false.

In the main function, we define a sample subsequence and main array and call the isSubsequence function to check if the subsequence is present in the main array. The result is printed to the console.

Note: This implementation assumes that the elements in the arrays are of the same type (int in this case). If you are working with arrays of a different data type, you may need to modify the code accordingly.