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744. Find Smallest Letter Greater Than Target - Easy

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"

 

Note:

  1. letters has a length in range [2, 10000].
  2. letters consists of lowercase letters, and contains at least 2 unique letters.
  3. target is a lowercase letter.

 

如果沒有比target大的元素,就返回陣列第一個元素

time: O(log(n)), space: O(1)

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