The simplest way to solve the problem is to iterate over the array and find the first character that is greater than the target character. If such a character is not found by the end of the array, the function should return the first character of the array. This approach simply checks each character in order from left to right, comparing it with the target.
Time Complexity: O(n) where n is the size of the array since each element may be checked in the worst case.
Space Complexity: O(1) as only a constant amount of space is used.
1def nextGreatestLetter(letters, target):
2 for letter in letters:
3 if letter > target:
4 return letter
5 return letters[0]This function straightforwardly checks each letter in the letters array to see if it exceeds target. If it finds such a letter, it returns it; otherwise, it defaults to the first letter.
Utilizing the sorted nature of the array, we can employ a binary search technique to pinpoint the smallest character that exceeds the target. By continually narrowing the search range, we can efficiently determine the desired character. If the binary search concludes without finding a suitable character, the array's initial character is returned.
Time Complexity: O(log n), hinging on halving the array.
Space Complexity: O(1), processing is constant-space.
1public class Solution {
2 public char NextGreatestLetter(char[] letters, char target) {
3 int low = 0, high = letters.Length - 1;
4 while (low <= high) {
5 int mid = low + (high - low) / 2;
6 if (letters[mid] <= target) {
7 low = mid + 1;
8 } else {
9 high = mid - 1;
10 }
11 }
12 return letters[low % letters.Length];
13 }
14}This C# solution engages a binary search within the string array. Once the span has sufficiently narrowed, it leverages a modulus to generate the resultant character, honoring the circular condition within the logic.