While i'm reading about STL iterators, this note found in <https://www.sgi.com/tech/stl/Iterators.html>

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> The most restricted sorts of iterators are Input Iterators and Output Iterators, both of which permit "single pass" algorithms but do not necessarily support "multi-pass" algorithms.
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1. What does the mean of "Single Pass Algorithms"
2. What does the mean of above sentence