1.     /**
    2.      * leetcode #744 寻找比目标字母大的最小字母
    3.      * 题目描述：给定一个有序的字符数组 letters 和一个字符 target，
    4.      * 要求找出 letters 中大于 target 的最小字符，如果找不到就返回第 1 个字符。
    5.      * 
    6.      * Input: letters = ["c", "f", "j"] target = "d"
    7.      * Output: "f"
    8.      * Input: letters = ["c", "f", "j"] target = "k"
    9.      * Output: "c"
    10.      **/
    11.     function nextGreatestLetter(letters, target) {
    12.       let l = 0, h = letters.length - 1;
    13.       let res = 0;
    14.       while (l <= h) {
    15.         let m = Math.floor((l + h) / 2)
    16.         if (letters[m] > target) {
    17.           res = m;
    18.           h = m - 1
    19.         } else {
    20.           l = m + 1
    21.         }
    22.       }
    23.       return letters[res]
    24.     }
    27.     console.log(nextGreatestLetter(["a", "b", "c", "d", "f", "j"], 'k'))