483. Identify the Peak Altitude

You are given a sorted array of integers representing altitudes measured at fixed intervals along a mountain trail. The trail starts at a low elevation, increases steadily to a single peak, and then decreases. However, you are only given the first half of this data: a strictly increasing sequence of integers. Your task is to find the index of the first altitude that is greater than or equal to a specific target value using a binary search approach. If no such altitude exists, return the length of the array.

Example:
Input: altitudes = [1200, 1500, 1800, 2100, 2500], target = 1900
Output: 3

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