Final answer:
In the maxHeapPercolateDown() function, 'int childIndex = 2 * nodeIndex + 1' is the correct line to find the left child index of a node in a max-heap. If the right child needs to be considered, the index is 'int childIndex = 2 * nodeIndex + 2'. Both child indexes must remain within the bounds of the array representing the heap.
Step-by-step explanation:
In the maxHeapPercolateDown() function, the goal is to maintain the max-heap property after a node's value becomes smaller than its children. To find the correct child index of the current node index during the percolation process, the following line is used: 'int childIndex = 2 * nodeIndex + 1'. This specific line ensures that we are pointing to the left child of the current node, following the property of a binary heap where the left child of a node at index i is at index 2*i + 1.
If the right child also needs to be considered—which is often the case in a max-heap to compare and determine the larger of the two children—the right child's index would be 'int childIndex = 2 * nodeIndex + 2'. It's essential to check if the child node indexes are within the bounds of the heap array to avoid accessing invalid memory locations.