744. Find Smallest Letter Greater Than Target

Given a sorted array of distinct integers and a target value, return the index if the target is found. If not, return the index where it would be if it were inserted in order.

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

Example 1:

Input: nums = [1,3,5,6], target = 5
Output: 2

Example 2:

Input: nums = [1,3,5,6], target = 2
Output: 1

Example 3:

Input: nums = [1,3,5,6], target = 7
Output: 4

Example 4:

Input: nums = [1,3,5,6], target = 0
Output: 0

Example 5:

Input: nums = [1], target = 0
Output: 0

Constraints:

• 1 <= nums.length <= 104
• -104 <= nums[i] <= 104
• nums contains distinct values sorted in ascending order.
• -104 <= target <= 104

class Solution {
    public char nextGreatestLetter(char[] letters, char target) {
        //if (letters[0] > target) return letters[0];
        if (letters[letters.length - 1] <= target) return letters[0];
        int l = 0, r = letters.length - 1;
        while(l <= r) {
            int m = l + (r - l) / 2;
            if(letters[m] > target) r = m - 1;
            else l = m + 1;
        }
        return letters[l];
    }
}