Binary search --- larger than the smallest element of a given element

Greater than the smallest element of the given element

744. Find Smallest Letter Greater Than Target (Easy)

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

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

Subject description:

  Given an ordered array of characters and a character target letters, asked to identify letters larger than the smallest character in the target, if not found returns the first character.

Analysis of ideas:

  Dichotomy to find.

Code:

public char nextGreatestLetter(char []letters,char target){
    if(letters==null||letters.length==0)
        return null;
    int len=letters.length;
    int l=0,h=n-1;
    while(l<=h){
        int mid=l+(h-l)/2;
        if(letters[mid]<=target){
            l=mid+1;
        }else{
            h=mid-1;
        }
    }
    return l<len?letters[l]:letters[0];
}