744. Find Smallest Letter Greater Than Target.java

/*
Given a characters array letters that is sorted in non-decreasing order and a character target, return the smallest character in the array that is larger than target.

Note that the letters wrap around.

For example, if target == 'z' and letters == ['a', 'b'], the answer is 'a'.
 

Example 1:

Input: letters = ["c","f","j"], target = "a"
Output: "c"
Example 2:

Input: letters = ["c","f","j"], target = "c"
Output: "f"
Example 3:

Input: letters = ["c","f","j"], target = "d"
Output: "f"
Example 4:

Input: letters = ["c","f","j"], target = "g"
Output: "j"
Example 5:

Input: letters = ["c","f","j"], target = "j"
Output: "c"
 

Constraints:

2 <= letters.length <= 104
letters[i] is a lowercase English letter.
letters is sorted in non-decreasing order.
letters contains at least two different characters.
target is a lowercase English letter.
*/
class Solution {
    public char nextGreatestLetter(char[] arr, char target) {
        int start = 0;
        int end = arr.length - 1;
        while (start <= end){
            int mid = start + (end - start) / 2;
            if(arr[mid] > target){
                end = mid-1;
            }else {
                start = mid + 1;
            }
        }

       if(start == arr.length){
           return arr[0];
       }
       return arr[start];

        //or we can do by this way also
      //  return arr[start % arr.length];
    }
}