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POhow would you ensure subscript element access is within the size limit of a heap container e.g vector in implementing a move_down_the_heap function?
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  1. POhow would you ensure subscript element access is within the size limit of a heap container e.g vector in implementing a move_down_the_heap function?
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    copied!<p>the interface looks like this </p> <pre><code>template &lt;class T, class Pred&gt; void downheap (std::vector&lt;T&gt;&amp; heap_vector, unsigned int startingIndex, Pred predicateFunc); </code></pre> <p>if the <em>startingIndex</em> is at <strong>k</strong> in the vector, its <strong>left child</strong> in the heap will be located at index <strong>(2 * k)</strong> and its <strong>right child</strong> in the heap will be located at index <strong>((2 * k )+ 1)</strong>. essentially, the item should be compared (and swapped as necessary) with its appropriate child in the heap until the given order by the predicate function has been satisfied.</p> <p>the predicate might be greaterthan, lesserthan or any custom sequence...</p> <p>in implementing such a method, how do you check that index access is within the size limit? i.e <strong>heap_vector[rightChildIndex]</strong> or <strong>heap_vector[leftChildIndex]</strong> should not go beyond <strong>heap_vector.size()-1</strong> while looping and doing comparison... it has given me a bit of a headache</p> <p>here is my code </p> <pre><code> while ( pred ( heap_vector[rightChild], heap_vector[parentIndex] ) || pred ( heap_vector[leftChild], heap_vector[parentIndex] ) ) { if ( pred ( heap_vector[rightChild], heap_vector[leftChild]) ) { std::swap(heap_vector[parentIndex],heap_vector[rightChild]); parentIndex=rightChild; } else { std::swap( heap_vector[parentIndex], heap_vector[leftChild]); parentIndex=leftChild; } rightChild= 2*parentIndex+1; leftChild=2*parentIndex; if (rightChild&gt;heap_vector.size() || leftChild&gt;heap_vector.size()) break; } </code></pre>
 

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