［抄題］：

Given a list of sorted characters letters containing only lowercase letters, and given a target letter target, find the smallest element in the list that is larger than the given target.

Letters also wrap around. For example, if the target is target = ‘z‘ and letters = [‘a‘, ‘b‘], the answer is ‘a‘

Examples:

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

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

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

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

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

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

[暴力解法]：

時間分析：

空間分析：

[優化後]：

時間分析：

空間分析：

［奇葩輸出條件］：

［奇葩corner case］：

Input:
letters = ["c", "f", "j"]
target = "k"
Output: "c"
結果是最後一位，但是需要返回第一位 結果%n （看余數 不止看倍數）

［思維問題］：

“第一個最大”居然沒看出來是二分查找問題。字母換成index數字後繼續操作啊

［一句話思路］：

［輸入量］：空： 正常情況：特大：特小：程序裏處理到的特殊情況：異常情況（不合法不合理的輸入）：

［畫圖］：

［一刷］：

［二刷］：

［三刷］：

［四刷］：

［五刷］：

[五分鐘肉眼debug的結果]：

［總結］：

“第一個最大”居然沒看出來是二分查找問題。字母換成index數字後繼續操作啊

［復雜度］：Time complexity: O(lgn) Space complexity: O(1)

［英文數據結構或算法，為什麽不用別的數據結構或算法］：

［關鍵模板化代碼］：

九章的不行就用這一套：

while (lo < hi)

lo = mid + 1

//Terminal condition is ‘lo < hi‘, to avoid infinite loop when target is smaller than the first element
        while (lo < hi) {
            int mid = lo + (hi - lo) / 2;
            if (a[mid] > x)     hi = mid;
            else    lo = mid + 1;                 //a[mid] <= x
        }

［其他解法］：

［Follow Up］：

［LC給出的題目變變變］：

[代碼風格] ：

class Solution {
    public char nextGreatestLetter(char[] letters, char target) {
        //ini
        int n = letters.length;
        int start = 0, end = n;
        
        //bs
        while (start < end) {
            int mid = start + (end - start) / 2;
            if (target < letters[mid]) {
                end = mid;
            }else {
                start = mid + 1;
            }
        }
        
        //return
        return letters[start % n];
    }
}

744. Find Smallest Letter Greater Than Target 查找比目標字母大的最小字母