advanced
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First Missing Positive
The array is not just input. Under the right invariant, it becomes its own presence map.
View solutioncore-pattern
Cyclic Sort & Index Placement
Exploit a value-to-index mapping to place elements naturally and expose missing, duplicate, or displaced values in place.
Problems
Problems in Cyclic Sort & Index Placement
Practice problems that share this primary solution pattern and compare the clues that reveal it.