P16278 「MierOI R1」Present

Two strings $a$ and $b$, both of length $m$, are called **isomorphic** if and only if: - For any $1 \le i,j \le m$, if $a_i=a_j$, then $b_i=b_j$; otherwise, $b_i \ne b_j$. Given two strings $s$ and $t$, both of length $n$. Among all strings $s'$ that are isomorphic to $s$, find the maximum number of pairs of **identical characters** at the **same positions** between $s'$ and $t$.

**This problem contains multiple test cases.** The first line of the input contains a positive integer $T$, indicating the number of test cases. Then, the $T$ test cases follow sequentially. For each test case: - The first line contains a single positive integer $n$. - The second line contains a string $s$ of length $n$. - The third line contains a string $t$ of length $n$.

For each test case, output a single line containing an integer, representing the maximum number of pairs of identical characters at the same positions between $s'$ and $t$.

#### Explanation for Sample #1 For the first test case, we can have $s'=\texttt{221133}$, and the number of pairs of identical characters at the same positions between it and $t=\texttt{221111}$ is $4$. It can be proven that this is the maximum number. For the second test case, we can have $s'=\texttt{1425314253}$, and the number of pairs of identical characters at the same positions between it and $t=\texttt{1122334455}$ is $5$. It can be proven that this is the maximum number. #### Data Range **This problem uses bundled subtasks.** For all test cases, it is guaranteed that $1 \le T \le 5$, $1 \le n \le 10^5$, and both $s$ and $t$ consist only of numeric characters. ::cute-table{tuack} | Subtask | $n \le$ | Special Property | Score | |:-:|:-:|:-:|:-:| | $1$ | $5$ | None | $30$ | | $2$ | $10^5$ | A | $30$ | | $3$ | ^ | None | $40$ | - Special Property A: Both $s$ and $t$ consist only of $\texttt{0},\texttt{1},\texttt{2},\texttt{3},\texttt{4}$.