O(n) time and O(1) space using linear search

744. Find Smallest Letter Greater Than Target/744. Find Smallest Letter Greater Than Target.py

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+'''
+You are given an array of characters letters that is sorted in non-decreasing order, and a character target. There are at least two different characters in letters.
+
+Return the smallest character in letters that is lexicographically greater than target. If such a character does not exist, return the first character in letters.
+
+
+
+Example 1:
+
+Input: letters = ["c","f","j"], target = "a"
+Output: "c"
+Explanation: The smallest character that is lexicographically greater than 'a' in letters is 'c'.
+Example 2:
+
+Input: letters = ["c","f","j"], target = "c"
+Output: "f"
+Explanation: The smallest character that is lexicographically greater than 'c' in letters is 'f'.
+Example 3:
+
+Input: letters = ["x","x","y","y"], target = "z"
+Output: "x"
+Explanation: There are no characters in letters that is lexicographically greater than 'z' so we return letters[0].
+
+
+Constraints:
+
+2 <= letters.length <= 104
+letters[i] is a lowercase English letter.
+letters is sorted in non-decreasing order.
+letters contains at least two different characters.
+target is a lowercase English letter.
+'''
+class Solution:
+    def nextGreatestLetter(self, letters: List[str], target: str) -> str:
+        result,diff = letters[0],sys.maxsize
+        for letter in letters:
+            cur_diff = ord(letter) - ord(target)
+            if cur_diff > 0 and cur_diff < diff:
+                diff = cur_diff
+                result = letter
+        return result