744. 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’.

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: 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.

#### SOLUTION：

``````class Solution {
public char nextGreatestLetter(char[] letters, char target) {
int[] index = new int[52];
for(char c:letters){
index[c-'a'] +=1;
index[c-'a'+26] +=1;
}
int cursor = target-'a'+1;
while (index[cursor]==0)
cursor++;
return (char)('a'+cursor%26);
}
}
``````