Is there any good tutorials on persistent data structures? ↵
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I've seen many solutions for [this](http://mirror.codeforces.com/contest/707/problem/D) problem, some uses bitwise trick and some used graphs and dfs which i don't really get how can it be applied to such a problem.↵
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Would any of you mind explaining his approach?↵
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Many Thanks .
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I've seen many solutions for [this](http://mirror.codeforces.com/contest/707/problem/D) problem, some uses bitwise trick and some used graphs and dfs which i don't really get how can it be applied to such a problem.↵
↵
Would any of you mind explaining his approach?↵
↵
Many Thanks
