LeetCode-in-Java

744. Find Smallest Letter Greater Than Target

Easy

Given a characters array letters that is sorted in non-decreasing order and a character target, return the smallest character in the array that is larger than target.

Note that the letters wrap around.

• For example, if target == 'z' and letters == ['a', 'b'], the answer is 'a'.

Example 1:

Input: letters = [“c”,”f”,”j”], target = “a”

Output: “c”

Example 2:

Input: letters = [“c”,”f”,”j”], target = “c”

Output: “f”

Example 3:

Input: letters = [“c”,”f”,”j”], target = “d”

Output: “f”

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.

Solution

public class Solution {
    public char nextGreatestLetter(char[] letters, char target) {
        int start = 0;
        int end = letters.length - 1;
        // If target is greater than last element return first element of the array.
        if (letters[letters.length - 1] <= target) {
            return letters[start];
        }
        while (start < end) {
            int mid = start + (end - start) / 2;
            if (letters[mid] <= target) {
                start = mid + 1;
            } else {
                end = mid;
            }
        }
        return letters[start];
    }
}

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