I tried to make this algorithm to work in C++ but I'm not getting any proper solution.

 the pseudocode of insertion into an Array List. Recall that we assume that all elements in the array must be contiguous. Also, note that the pseudocode uses 0-based indexing.

insert(element, index): // inserts element into array and returns True on success (or False on failure)
    // perform the required safety checks before insertion
    if index < 0 or index > n:   // invalid indices
        return False

    if n == array.length:        // if array is full
        newArray = empty array of length 2*array.length
        for i from 0 to n-1:     // copy all elements of old array to new array
            newArray[i] = array[i]
        array = newArray         // replace old array with new array

    // perform the insertion algorithm
    if index == n:               // insertion at end of array
        array[index] = element   // perform insertion

    else:                        // general insertion
        for i from n-1 to index: // make space for the new element (if insertion not at the end)
            array[i+1] = array[i]
        array[index] = element   // perform insertion

    n = n+1                      // increment number of elements
    return True