CF1714B.Remove Prefix

Polycarp was presented with some sequence of integers $a$ of length $n$ ($1 \le a_i \le n$). A sequence can make Polycarp happy only if it consists of different numbers (i.e. distinct numbers).

In order to make his sequence like this, Polycarp is going to make some (possibly zero) number of moves.

In one move, he can:

• remove the first (leftmost) element of the sequence.

For example, in one move, the sequence $[3, 1, 4, 3]$ will produce the sequence $[1, 4, 3]$, which consists of different numbers.

Determine the minimum number of moves he needs to make so that in the remaining sequence all elements are different. In other words, find the length of the smallest prefix of the given sequence $a$, after removing which all values in the sequence will be unique.

波利卡普收到了一个长度为 $n$ 的整数序列 $a$（其中 $1 \le a_i \le n$）。仅当该序列由互不相同的数字（即所有元素互异）组成时，该序列才能令波利卡普满意。

为了使序列满足这一条件，波利卡普将进行若干次（可能为零次）操作。

每次操作中，他可以：

• 删除序列最前面（最左侧）的元素。

例如，对序列 $[3, 1, 4, 3]$ 执行一次操作后，得到序列 $[1, 4, 3]$，其所有元素互不相同。

请确定波利卡普所需的最少操作次数，使得剩余序列中所有元素互异。换言之，求出需从给定序列 $a$ 中删除的最短前缀的长度，使得删除该前缀后，序列中所有数值均唯一。

The first line of the input contains a single integer $t$ ($1 \le t \le 10^4$) — the number of test cases.

Each test case consists of two lines.

The first line contains an integer $n$ ($1 \le n \le 2 \cdot 10^5$) — the length of the given sequence $a$.

The second line contains $n$ integers $a_1, a_2, \dots, a_n$ ($1 \le a_i \le n$) — elements of the given sequence $a$.

It is guaranteed that the sum of $n$ values over all test cases does not exceed $2 \cdot 10^5$.

输入的第一行包含一个整数 $t$（$1 \le t \le 10^4$）—— 表示测试用例的数量。

每个测试用例由两行组成。

第一行包含一个整数 $n$（$1 \le n \le 2 \cdot 10^5$）—— 表示给定序列 $a$ 的长度。

第二行包含 $n$ 个整数 $a_1, a_2, \dots, a_n$（$1 \le a_i \le n$）—— 表示给定序列 $a$ 的元素。

保证所有测试用例的 $n$ 值之和不超过 $2 \cdot 10^5$。

For each test case print your answer on a separate line — the minimum number of elements that must be removed from the beginning of the sequence so that all remaining elements are different.

对于每个测试用例，在单独一行输出你的答案——即：为使剩余所有元素互不相同，必须从序列开头移除的最少元素个数。

The following are the sequences that will remain after the removal of prefixes:

• $[1, 4, 3]$;
• $[1]$;
• $[1]$;
• $[6, 5, 4, 3, 2, 1]$;
• $[2, 1]$.

It is easy to see that all the remaining sequences contain only distinct elements. In each test case, the shortest matching prefix was removed.

以下是在移除前缀后剩余的序列：

• $[1, 4, 3]$；
• $[1]$；
• $[1]$；
• $[6, 5, 4, 3, 2, 1]$；
• $[2, 1]$。

容易看出，所有剩余序列均仅包含互异的元素。在每个测试用例中，被移除的均为最短的匹配前缀。