Find the First Occurrence Index in a Sorted Array with Duplicates

Problem Given a non-decreasing sorted integer array nums (may contain duplicates) and an integer target, return the index of the first occurrence of target in the array. If target does not exist, return -1. I/O Input: array nums, integer target Output: an integer index of the leftmost (first) occurrence Constraints 1 <= len(nums) <= 2 * 10^5 nums is sorted in non-decreasing order nums[i] and target fit in 32-bit signed integer Expected time complexity: O(log n) Examples nums = [1, 3, 5, 8, 8, 8, 8, 8, 9, 10, 15], target = 8 → 3 nums = [1,2,3], target = 4 → -1 Example Input 11 1 3 5 8 8 8 8 8 9 10 15 8 Output 3