Minimum Operations to Make Array Equal

Problem Overview

• Core task: Find the minimum operations to turn array source into target by choosing any even-length subarray and alternately adding and subtracting 1 across it.
• Inputs/outputs: Two integer arrays of length n; output the minimal operation count, or -1 if it cannot be made equal.
• Constraints: 1 ≤ n ≤ 1e5; elements range from -1e9 to 1e9.
• Context: Array manipulation and data transformation problem for a coding interview; a common interview question from Deshaw interviews.