# 744 Find Smallest Letter Greater Than Target

### Problem

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:

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

### Solutions

``````class Solution {
public char nextGreatestLetter(char[] letters, char target) {
Character minInGreater = null;
Character min = null;
for (int i = 0; i < letters.length; i ++) {
char c = letters[i];
if (min == null || c < min) {
min = c;
}
if (c > target && (minInGreater == null || c < minInGreater)) {
minInGreater = c;
}
}
return minInGreater == null? min:minInGreater;
}
}
``````
``````class Solution {
public char nextGreatestLetter(char[] letters, char target) {
int left = 0, right = letters.length - 1;
while (left <= right) {
int mid = left + (right - left) / 2;
if (letters[mid] <= target) {
left ++;
}
else {
right --;
}
}
if (left == letters.length) {
return letters;
}
return letters[left];
}
}
``````