Find the largest Alphabetic character present in the string - GeeksforGeeks

08 Sep, 2021
Given a string str, our task is to find the Largest Alphabetic Character, whose both uppercase and lowercase are present in the string. The uppercase character should be returned. If there is no such character then return -1 otherwise print the uppercase letter of the character.
Examples: 
Input: str = “admeDCAB” Output: D Explanation: Both the uppercase and lowercase characters for letter D is present in the string and it is also the largest alphabetical character, hence our output is D.
Input: str = “dAeB” Output: -1 Explanation: Although the largest character is d in the string but the uppercase version is not present hence the output is -1. 
Naive Approach: To solve the problem mentioned above the naive method is to check for the presence of each character in the string for both uppercase or lowercase character that is for letter A both ‘a’ and ‘A’ should be there in the string. If such a letter is present then will keep track of that character and update only if the current character is greater than the previously chosen character. This method takes O(n2) time in the worst case and can be further optimized.
Efficient Approach: To optimize the above method we use the fact that we have 26 characters in the English alphabet, we can keep track of both lowercase and uppercase character by maintaining an array of size 26. While iterating through the given string we will mark true in both the array if the current character is present in both uppercase and lowercase letter. After marking all characters present in the respective array we will run a loop from 25 to 0 and check if both the array has ‘true’ marked in them. If yes then we print the uppercase letter of that character otherwise return -1.
Below is the implementation of the above approach: 
Java
Python3
C#
Javascript
// Java program to Find the Largest Alphabetic// Character present in the string of both// uppercase and lowercase English characters public class Main {     // Function to find the Largest Alphabetic Character    public static String largestCharacter(String str)    {        // Array for keeping track of both uppercase        // and lowercase english alphabets        boolean[] uppercase = new boolean[26];        boolean[] lowercase = new boolean[26];         char[] arr = str.toCharArray();         for (char c : arr) {             if (Character.isLowerCase(c))                lowercase = true;             if (Character.isUpperCase(c))                uppercase = true;        }         // Iterate from right side of array        // to get the largest index character        for (int i = 25; i >= 0; i--) {             // Check for the character if both its            // uppercase and lowercase exist or not            if (uppercase[i] && lowercase[i])                return (char)(i + 'A') + "";        }         // Return -1 if no such character whose        // uppercase and lowercase present in        // string str        return "-1";    }     // Driver code    public static void main(String[] args)    {        String str = "admeDCAB";         System.out.println(largestCharacter(str));    }}
# Java program to Find the Largest Alphabetic# Character present in the string of both# uppercase and lowercase English characters # Function to find the Largest Alphabetic Characterdef largestCharacter(str):         # Array for keeping track of both uppercase    # and lowercase english alphabets    uppercase = [False] * 26    lowercase = [False] * 26         arr = list(str)    for c in arr:        if (c.islower()):            lowercase[ord(c) - ord('a')] = True        if (c.isupper()):            uppercase[ord(c) - ord('A')] = True                 # Iterate from right side of array    # to get the largest index character    for i in range(25,-1,-1):                 # Check for the character if both its        # uppercase and lowercase exist or not        if (uppercase[i] and lowercase[i]):            return chr(i + ord('A')) + ""    # Return -1 if no such character whose    # uppercase and lowercase present in    # string str    return "-1" # Driver code str = "admeDCAB"print(largestCharacter(str))      # This code is contributed by shivanisinghss2110
// C# program to Find the Largest Alphabetic// char present in the string of both// uppercase and lowercase English charactersusing System; class GFG{   // Function to find the Largest Alphabetic charpublic static String largestchar(String str){         // Array for keeping track of both uppercase    // and lowercase english alphabets    bool[] uppercase = new bool[26];    bool[] lowercase = new bool[26];     char[] arr = str.ToCharArray();     foreach(char c in arr)    {        if (char.IsLower(c))            lowercase = true;         if (char.IsUpper(c))             uppercase = true;    }     // Iterate from right side of array    // to get the largest index character    for(int i = 25; i >= 0; i--)    {                 // Check for the character if both its        // uppercase and lowercase exist or not        if (uppercase[i] && lowercase[i])            return (char)(i + 'A') + "";    }     // Return -1 if no such character whose    // uppercase and lowercase present in    // string str    return "-1";} // Driver codepublic static void Main(String[] args){    String str = "admeDCAB";     Console.WriteLine(largestchar(str));}}  // This code is contributed by amal kumar choubey
<script>     // JavaScript program to Find the Largest Alphabetic    // Character present in the string of both    // uppercase and lowercase English characters         // Function to find the Largest Alphabetic Character    function largestCharacter(str)    {        // Array for keeping track of both uppercase        // and lowercase english alphabets        let uppercase = new Array(26);        uppercase.fill(false);        let lowercase = new Array(26);        lowercase.fill(false);          let arr = str.split('');          for (let c = 0; c < arr.length; c++) {              if (arr == arr.toLowerCase())                lowercase[arr.charCodeAt() - 97] = true;              if (arr == arr.toUpperCase())                uppercase[arr.charCodeAt() - 65] = true;        }          // Iterate from right side of array        // to get the largest index character        for (let i = 25; i >= 0; i--) {              // Check for the character if both its            // uppercase and lowercase exist or not            if (uppercase[i] && lowercase[i])                return String.fromCharCode(i +                'A'.charCodeAt()) + "";        }          // Return -1 if no such character whose        // uppercase and lowercase present in        // string str        return "-1";    }         let str = "admeDCAB";      document.write(largestCharacter(str)); </script>
Output:
D
Time complexity: O(n) where n is length of string. Space complexity: O(52) 
Amal Kumar Choubey
suresh07
surindertarika1234
shivanisinghss2110
Microsoft
Strings
Microsoft
Strings
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