10461: USACO 2024 US Open Contest, Bronze Problem 1. Logical Moos
Description
A phrase of the form $x\text{ OPERATOR }y$, where $x$ and $y$ are either $\texttt{true}$ or $\texttt{false}$, and $\text{OPERATOR}$ is $\texttt{and}$ or $\texttt{or}$, evaluates as follows:
- $x\texttt{ and }y$: This evaluates to true if both $x$ and $y$ are true, and false otherwise.
- $x\texttt{ or }y$: This evaluates to true if either $x$ or $y$ is true, and false otherwise.
When evaluating the statement, FJ has to take the order of precedence in Moo Language into account. Similar to C++, $\texttt{and}$ takes priority over $\texttt{or}$. More specifically, to evaluate the statement, repeat the following step until the statement consists of only one keyword.
- If the statement contains an $\texttt{and}$, choose any of them and replace the phrase surrounding it with its evaluation.
- Otherwise, the statement contains an $\texttt{or}$. Choose any of them and replace the phrase surrounding it with its evaluation.
It may be proven that if multiple phrases can be evaluated during a given step, it does not matter which one is chosen; the statement will always evaluate to the same value.
FJ has $Q$ $(1 \leq Q \leq 2 \cdot 10^5)$ queries. In each query, he gives you two integers $l$ and $r$ ($1 \leq l \leq r \leq N$, $l$ and $r$ are both odd), and deletes the segment from keyword $l$ to keyword $r$ inclusive. In turn, he wishes to replace the segment he just deleted with just one simple $\texttt{true}$ or $\texttt{false}$ so that the whole statement evaluates to a certain boolean value. Help FJ determine if it's possible!
Input
The next line contains $N$ strings, a valid boolean statement.
The following $Q$ lines contain two integers $l$ and $r$, and a string $\texttt{true}$ or $\texttt{false}$, denoting whether he wants the whole statement to evaluate to true or false.
Output
Constraints
- Inputs 3-5: $N,Q\le 10^2$
- Inputs 6-8: $N,Q\le 10^3$
- Inputs 9-26: No additional constraints.
Sample 1 Input
5 7
false and true or true
1 1 false
1 3 true
1 5 false
3 3 true
3 3 false
5 5 false
5 5 true
Sample 1 Output
NYYYNYY
If we were to replace delete the segment $[1, 1]$ and replace it with $\texttt{true}$, then the whole statement becomes:
true and true or true
We evaluate the $\texttt{and}$ keyword from at position $2$ and obtain
true or true
Since we have no $\texttt{and}$ keywords left, we have to evaluate the $\texttt{or}$ keyword. After evaluation, all that is left is
true
It can be shown that if we were to replace the segment with $\texttt{false}$, the statement will still evaluate to $\texttt{true}$, so we output N since the statement cannot possibly evaluate to $\texttt{false}$.
For the second query, we can replace the segment $[1, 3]$ with $\texttt{true}$ and the whole statement will evaluate to $\texttt{true}$, so we output Y.
For the third query, since $[1, 5]$ is the whole statement, we can replace it with anything, so we output Y.
Sample 2 Input
13 4
false or true and false and false and true or true and false
1 5 false
3 11 true
3 11 false
13 13 true
Sample 2 Output
YNYY