https://leetcode.com/problems/find-first-and-last-position-of-element-in-sorted-array/

find-first-and-last-position-of-element-in-sorted-array.java

class Solution {
    public int[] searchRange(int[] nums, int target) {
        if (nums == null || nums.length == 0) {
            return new int[]{-1, -1};
        }
        int l = findFirst(nums, target);
        int r = findLast(nums, target);
        
        return new int[]{l, r};
    }
    
    private int findFirst(int[] nums, int target) {
        int l = 0;
        int r = nums.length - 1;
        
        while(l < r) {
            int mid = l + (r - l) / 2;
            if (nums[mid] > target) {
                r = mid - 1;
            } else if (nums[mid] < target) {
                l = mid + 1;
            } else {
                r = mid;
            }
        }
        if (nums[l] == target) {
            return l;
        }
        return -1;
    }
    
    private int findLast(int[] nums, int target) {
        int l = 0;
        int r = nums.length - 1;
        
        while(l < r) {
            int mid = l + (r - l - 1) / 2 + 1;   // (l + r + 1) / 2;
            if (nums[mid] > target) {
                r = mid - 1;
            } else if (nums[mid] > target) {
                l = mid + 1;
            } else {
                l = mid;
            }
        }
        if (nums[l] == target) {
            return l;
        }
        return -1;
    }
    
    
}