# Tag Info

### Real life examples of negative weight edges in graphs

Distance between cities can't be negative, but if you are programming for an electric car, then a downhill road segment will regen, thus the energy used is negative. It is very important to take that ...
• 13.2k
Accepted

### Double exponentials vs single exponentials

The issue comes down to ambiguous terminology. $(a^b)^c = a^{bc}$, but $a^{(b^c)} \neq a^{bc}$. In other words, exponents aren't associative. Conventionally, nested exponentials without parentheses ...
• 6,920

### Real life examples of *zero* weight edges in graphs

Of course. The weight can mean things that are irrelevant to the existence of an edge. Since you don't ask for a "list of say 6 or 7 real-life examples", I will just add one. Consider a ...
• 13.2k

### Double exponentials vs single exponentials

$a^{(b^c)}$ is not the same as $(a^b)^c$. When people write $2^{2^k}$, they usually mean $2^{(2^k)}$, not $(2^2)^k$.
• 140k
Accepted

### How to solve a recurrence relation with a sum?

Here are several ways to solve your recurrence relation. Guessing Anyone with enough experience in computer science might recognize your recurrence as the one satisfied by $T(n) = 2^n$. Given this ...
• 268k

### Arrange in increasing order of asymptotic complexity

You have mistake in $(2.1)^n \cdot n^2<2^n \cdot n^3$, because it is equivalent $\left(\frac{2.1}{2}\right)^n<n$
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Accepted

### Finite representations and programming languages Countably inifite

Here is a simpler situation highlighting the difference. The set of finite binary strings is countable. The set of infinite binary strings is uncountable. Another example: the set of numbers with ...
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### What's wrong with this problem (Inclusion-Exclusion principle)

Let $A$, $B$, and $C$ be the set of pupils that have access to a PC running Windows, Apple, and Linux, respectively. We know that \begin{align*} |A \cup B \cup C| &= 120 \\ |A| &= 80 \\ ...
• 808
Accepted

### Application of set theory subjects as ordinals, forcing, generic filters in software engineering

The areas of set theory you refer to are generally rather abstract and don't seem to have a lot of applications. Also, the concept of "application" is different in math than in CS. Anyway, though ...
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Notice that with the mod operator ($\%$), you're using integer division, much as you are when you use the division operator ($/$) with two ints (at least in most (...