Lecture 018

Representation Invariants

To prevent overflow

Data structure invariant

Shape Invariant

we don't need to do anything, array took care

Using negation to compute order invariants

notice we don't need to compare i1 and i2

Checking the Order

for every child, parent is okay

pq_add proves

safety
weakening invariant for correctness show that there are at least 1 violation

is_heap_except_up

ensures there is at most one violation at the parent
as we swap, we move the one violation from down to up
after swap, there might or might not be violation

Grandparent check

Extra Specification Summary

Implementation of remove:

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