Find_First_and_Last.java

// Given an array of integers nums sorted in non-decreasing order, find the starting and ending position of a given target value.

// If target is not found in the array, return [-1, -1].

// You must write an algorithm with O(log n) runtime complexity.

class Solution {
    public int[] searchRange(int[] nums, int target) {
       int[] result = {-1, -1};
        int leftIndex = binarySearch(nums, target, true);
        int rightIndex = binarySearch(nums, target, false);
        if (leftIndex <= rightIndex) {
            result[0] = leftIndex;
            result[1] = rightIndex;
        }
        return result;
    }
    
    private int binarySearch(int[] nums, int target, boolean left) {
        int low = 0;
        int high = nums.length - 1;
        int index = -1;
        while (low <= high) {
            int mid = low + (high - low) / 2;
            if (nums[mid] == target) {
                index = mid;
                if (left) {
                    high = mid - 1;
                } else {
                    low = mid + 1;
                }
            } else if (nums[mid] < target) {
                low = mid + 1;
            } else {
                high = mid - 1;
            }
        }
        return index;
    }
}