Q744 Find Smallest Letter Greater Than Target

Find Smallest Letter Greater Than Target

Question

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'.

Example 1:

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:

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

Approach 1: Linear Search

Intuition and Algorithm

class Solution(object):
    def nextGreatestLetter(self, letters, target):
        for l in letters:
            if l > target:
                return l
        return letters[0]

def main():
    letters = ["c", "f", "j"]
    target = "j"
    solution=Solution().nextGreatestLetter(letters,target)
    print(solution)


if __name__ == "__main__":
    main()

Complexity Analysis

• Time complexity : .
• Space complexity : since it's a constant space solution.
• Runtime: 72 ms, faster than 99.40% of Python online submissions for Find Smallest Letter Greater Than Target.
• Memory Usage: 13.8 MB, less than 33.33% of Python online submissions for Find Smallest Letter Greater Than Target.