P04 — Order statistics — every solution explained

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• 1. How many elements are strictly less than v
• 2. How many strictly greater
• 3. Elements with equal counts of smaller and larger ("balanced" positions)
• 4. Rank of v = 1 + how many are strictly smaller
• 5. k-th smallest (1-based) via sorting a copy
• 6. Second largest DISTINCT value; Integer.MIN_VALUE if none
• 7. Median; even length -> average of the two middles, truncating
• 8. Is the array a permutation of 1..n?
• 9. Leader elements: every element to the right is strictly smaller. (Named by a dated 2025 candidate report.) Scan from the right
• 10. Equilibrium index: sum of the left part equals sum of the right part