Final answer:
The heapsort algorithm's running time is primarily influenced by the size of the input array, which determines the number of comparison and swap operations required.
Step-by-step explanation:
The primary factor influencing the running time of the heapsort algorithm is the size of the input array. Heapsort is a comparison-based sorting technique and involves organizing the input array into a heap data structure. The complexity of heapsort is O(n log n), where n is the number of elements in the array.
This is due to the process of constructing the heap and then repeatedly removing the largest element from the heap and reconstructing the heap until it is empty. The number of comparison and swap operations required is also dependent on the size of the input array, which influences the total time complexity of the sorting process.