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by Sumit Chourasia | Oct 03, 2020 | Category :coding | Tags : algorithm binary-search data-structure easy leetcode

Find Smallest Letter Greater Than Target - Array - Easy - LeetCode

Find Smallest Letter Greater Than Target - Array - Easy - LeetCode

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 Solution {
    public char NextGreatestLetter(char[] letters, char target) {        
        if(target>=letters[letters.Length-1]){
            return letters[0];
        }
        
        int low = 0;
        int high = letters.Length-1;        
        while(low<high){            
            int mid = low + (high-low)/2;            
            if(letters[mid]<=target){
                low = mid+1;
            }
            else{
                high=mid;
            }
                      
        }        
        
        return letters[high];
    }
}

Time Complexity: O(logn)

Space Complexity: O(1)

Contributed By: Sumit Chourasia
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