Array Sorting Binary Search
Learner Level

Implement the method firstOccurrence that returns the first index of a target value in a sorted array.

Given a sorted integer array, return the first zero-based index where target appears.

The task is designed to test careful handling of edge cases, not only the most common input.

  • Use only the first size elements.
  • The array may contain duplicate values.
  • Return -1 when the target is missing.

Example 1

Input
nums (int[]) = [1,2,2,2,3]
size (int) = 5
target (int) = 2
Returns (int) 1

Example 2

Input
nums (int[]) = [4,5,6]
size (int) = 3
target (int) = 7
Returns (int) -1

Example 3

Input
nums (int[]) = [9,9,9]
size (int) = 3
target (int) = 9
Returns (int) 0

Use binary search. When a match is found, store it and keep searching the left half.

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