README_EN.md

744. Find Smallest Letter Greater Than Target

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Description

You are given an array of characters letters that is sorted in non-decreasing order, and a character target. There are at least two different characters in letters.

Return the smallest character in letters that is lexicographically greater than target. If such a character does not exist, return the first character in letters.

 

Example 1:

Input: letters = ["c","f","j"], target = "a"
Output: "c"
Explanation: The smallest character that is lexicographically greater than 'a' in letters is 'c'.

Example 2:

Input: letters = ["c","f","j"], target = "c"
Output: "f"
Explanation: The smallest character that is lexicographically greater than 'c' in letters is 'f'.

Example 3:

Input: letters = ["x","x","y","y"], target = "z"
Output: "x"
Explanation: There are no characters in letters that is lexicographically greater than 'z' so we return letters[0].

 

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.

Solutions

Python3

class Solution:
    def nextGreatestLetter(self, letters: List[str], target: str) -> str:
        left, right = 0, len(letters)
        while left < right:
            mid = (left + right) >> 1
            if ord(letters[mid]) > ord(target):
                right = mid
            else:
                left = mid + 1
        return letters[left % len(letters)]

Java

class Solution {
    public char nextGreatestLetter(char[] letters, char target) {
        int left = 0, right = letters.length;
        while (left < right) {
            int mid = (left + right) >> 1;
            if (letters[mid] > target) {
                right = mid;
            } else {
                left = mid + 1;
            }
        }
        return letters[left % letters.length];
    }
}

TypeScript

function nextGreatestLetter(letters: string[], target: string): string {
    const n = letters.length;
    let left = 0;
    let right = letters.length;
    while (left < right) {
        let mid = (left + right) >>> 1;
        if (letters[mid] > target) {
            right = mid;
        } else {
            left = mid + 1;
        }
    }
    return letters[left % n];
}

C++

class Solution {
public:
    char nextGreatestLetter(vector<char>& letters, char target) {
        int left = 0, right = letters.size();
        while (left < right) {
            int mid = left + right >> 1;
            if (letters[mid] > target) {
                right = mid;
            } else {
                left = mid + 1;
            }
        }
        return letters[left % letters.size()];
    }
};

Go

func nextGreatestLetter(letters []byte, target byte) byte {
	left, right := 0, len(letters)
	for left < right {
		mid := (left + right) >> 1
		if letters[mid] > target {
			right = mid
		} else {
			left = mid + 1
		}
	}
	return letters[left%len(letters)]
}

Rust

impl Solution {
    pub fn next_greatest_letter(letters: Vec<char>, target: char) -> char {
        *letters.iter().find(|&&c| c > target).unwrap_or(&letters[0])
    }
}

impl Solution {
    pub fn next_greatest_letter(letters: Vec<char>, target: char) -> char {
        let n = letters.len();
        let mut left = 0;
        let mut right = n;
        while left < right {
            let mid = left + (right - left) / 2;
            if letters[mid] > target {
                right = mid;
            } else {
                left = mid + 1;
            }
        }
        letters[left % n]
    }
}

PHP

class Solution {
    /**
     * @param String[] $letters
     * @param String $target
     * @return String
     */
    function nextGreatestLetter($letters, $target) {
        $left = 0;
        $right = count($letters);
        while ($left <= $right) {
            $mid = floor($left + ($right - $left) / 2);
            if ($letters[$mid] > $target) {
                $right = $mid - 1;
            } else {
                $left = $mid + 1;
            }
        }
        if ($left >= count($letters)) {
            return $letters[0];
        } else {
            return $letters[$left];
        }
    }
}

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