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NextLetterGreaterThanTarget.java
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NextLetterGreaterThanTarget.java
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package Leetcode;
/**
* @author kalpak
*
* 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.
*
*/
public class NextLetterGreaterThanTarget {
public static char nextGreatestLetter(char[] letters, char target) {
int left = 0;
int right = letters.length - 1;
char result = '#';
while (left <= right) {
int mid = left + (right - left)/2;
if(letters[mid] == target) {
left = mid + 1;
}
else if (letters[mid] < target) {
left = mid + 1;
} else if (letters[mid] > target) {
right = mid - 1;
result = letters[mid];
}
}
return (left >= letters.length) ? letters[0] : result; // wrap around if letter to be added in the end
}
public static void main(String[] args) {
char[] letters = new char[]{'c', 'f', 'j'};
System.out.println(nextGreatestLetter(letters, 'a'));
System.out.println(nextGreatestLetter(letters, 'c'));
System.out.println(nextGreatestLetter(letters, 'd'));
System.out.println(nextGreatestLetter(letters, 'j'));
System.out.println(nextGreatestLetter(letters, 'k'));
}
}