InsertAt

InsertAt is a programming operation that inserts a new element at a specified position within a sequence. The operation typically shifts existing elements to accommodate the new item and is defined for mutable sequences such as arrays and lists, as well as buffers and strings in some languages. The exact form of the operation varies by language, but insertAt is a common naming convention for a function or method that takes at least two parameters: the index and the value to insert. In zero-based indexing, index 0 inserts at the start; in one-based contexts, index 1 would do so.

In arrays, insertion is usually O(n) because elements must be shifted to make room for the new item. In linked lists, inserting at a position can be O(i) to reach the position, then O(1) to perform the insertion. Immutable data structures may return a new sequence with the element inserted rather than modifying the original. Some languages offer alternative names for the same concept, such as insert, splice, or add at a position, depending on the data type and library design.

Common language examples illustrate the idea. Python uses lst.insert(index, value) to mutate the list, e.g., [1, 2, 3] with lst.insert(2, 'a') becomes [1, 2, 'a', 3]. JavaScript provides arr.splice(index, 0, value) to insert without removing elements. Java’s List interface uses add(index, element) for List implementations like ArrayList. In C++, vec.insert(vec.begin() + index, value) handles vectors, while std::list uses insert(it, value) with an iterator.

Edge cases include inserting at the start (index 0), at the end (index equal to length, which often appends), or at an out-of-bounds index, which may throw an error or clamp depending on the language. See also insert and splice for related operations.