Prefixing

Given an array $A$ of size $N$, construct an array $B$ of size $N$ such that : - Every element of $B$ is present **at least once** in $A$; - For all $1\le i \le N$, every element in prefix $[A_1,A_2, \ldots, A_i]$ is present **at least once** in prefix $[B_1,B_2,\ldots, B_i]$. If multiple such arrays $B$ exist, find the **lexicographically largest** $B$. Note that for two arrays $X$ and $Y$, eac