Maximum occurring lexicographically smallest character in a String

Given a string containing lowercase characters. The task is to print the maximum occurring character in the input string. If 2 or more characters appear the same number of times, print the lexicographically (alphabetically) lowest (first) character.

Examples:

Input: test sample 
Output: e 
Explanation: e’t’, ‘e’ and ‘s’ appears 2 times, but ‘e’ is the lexicographically smallest character. 

Input: sample program
Output: a

In the previous article, if there are more than one character occurring the maximum number of time, then any of the characters is returned. In this post, the lexicographically smallest character of all the characters is returned.
Approach: Declare a freq[26] array which is used as a hash table to store the frequencies of each character in the input string. Iterate in the string and increase the count of freq[s[i]] for every character. Traverse the freq[] array from left to right and keep track of the character having the maximum frequency so far. The value at freq[i] represents the frequency of character (i + ‘a’).

Below is the implementation of the above approach: 

C++

// C++ implementation to find
// the maximum occurring character in
// an input string which is lexicographically first
#include <bits/stdc++.h>
using namespace std;

// function to find the maximum occurring character in
// an input string which is lexicographically first
char getMaxOccurringChar(char str[])
{
    // freq[] used as hash table
    int freq[26] = { 0 };

    // to store maximum frequency
    int max = -1;

    // to store the maximum occurring character
    char result;

    // length of 'str'
    int len = strlen(str);

    // get frequency of each character of 'str'
    for (int i = 0; i < len; i++)
        freq[str[i] - 'a']++;

    // for each character, where character is obtained by
    // (i + 'a') check whether it is the maximum character
    // so far and accordingly update 'result'
    for (int i = 0; i < 26; i++)
        if (max < freq[i]) {
            max = freq[i];
            result = (char)(i + 'a');
        }

    // maximum occurring character
    return result;
}

// Driver Code
int main()
{
    char str[] = "sample program";
    cout << "Maximum occurring character = "
         << getMaxOccurringChar(str);
    return 0;
}

Java

// Java implementation to find
// the maximum occurring character in
// an input string which is lexicographically first

class GFG {

// function to find the maximum occurring character in
// an input string which is lexicographically first
    static char getMaxOccurringChar(char str[]) {
        // freq[] used as hash table
        int freq[] = new int[26];

        // to store maximum frequency
        int max = -1;

        // to store the maximum occurring character
        char result = 0;

        // length of 'str'
        int len = str.length;

        // get frequency of each character of 'str'
        for (int i = 0; i < len; i++) {
            if (str[i] != ' ') {
                freq[str[i] - 'a']++;
            }
        }

        // for each character, where character is obtained by
        // (i + 'a') check whether it is the maximum character
        // so far and accordingly update 'result'
        for (int i = 0; i < 26; i++) {
            if (max < freq[i]) {
                max = freq[i];
                result = (char) (i + 'a');
            }
        }

        // maximum occurring character
        return result;
    }

// Driver Code
    public static void main(String[] args) {
        char str[] = "sample program".toCharArray();
        System.out.println("Maximum occurring character = "
                + getMaxOccurringChar(str));
    }
}

// This code is contributed by 29AjayKumar

Python3

# Python 3 implementation to find the
# maximum occurring character in an input
# string which is lexicographically first

# function to find the maximum occurring
# character in an input string which is
# lexicographically first
def getMaxOccurringChar(str):

    # freq[] used as hash table
    freq = [0 for i in range(100)]

    # to store maximum frequency
    max = -1

    # to store the maximum occurring
    # character length of 'str'
    len__ = len(str)

    # get frequency of each character of 'str'
    for i in range(0, len__, 1):
        freq[ord(str[i]) - ord('a')] += 1

    # for each character, where character
    # is obtained by (i + 'a') check whether
    # it is the maximum character so far and
    # accordingly update 'result'
    for i in range(26):
        if (max < freq[i]):
            max = freq[i]
            result = chr(ord('a') + i)

    # maximum occurring character
    return result

# Driver Code
if __name__ == '__main__':
    str = "sample program"
    print("Maximum occurring character =",
                 getMaxOccurringChar(str))

# This code is contributed by
# Surendra_Gangwar

C#

// C# implementation to find
// the maximum occurring character in
// an input string which is lexicographically first

using System;
class GFG {

// function to find the maximum occurring character in
// an input string which is lexicographically first
    static char getMaxOccurringChar(string str) {
        // freq[] used as hash table
        int[] freq = new int[26];

        // to store maximum frequency
        int max = -1;

        // to store the maximum occurring character
        char result = (char)0;

        // length of 'str'
        int len = str.Length;

        // get frequency of each character of 'str'
        for (int i = 0; i < len; i++) {
            if (str[i] != ' ') {
                freq[str[i] - 'a']++;
            }
        }

        // for each character, where character is obtained by
        // (i + 'a') check whether it is the maximum character
        // so far and accordingly update 'result'
        for (int i = 0; i < 26; i++) {
            if (max < freq[i]) {
                max = freq[i];
                result = (char) (i + 'a');
            }
        }

        // maximum occurring character
        return result;
    }

// Driver Code
    public static void Main() {
        string str = "sample program";
        Console.WriteLine("Maximum occurring character = "
                + getMaxOccurringChar(str));
    }
}

Javascript

// C# implementation to find
// the maximum occurring character in
// an input string which is lexicographically first

using System;
class GFG {

// function to find the maximum occurring character in
// an input string which is lexicographically first
    static char getMaxOccurringChar(string str) {
        // freq[] used as hash table
        int[] freq = new int[26];

        // to store maximum frequency
        int max = -1;

        // to store the maximum occurring character
        char result = (char)0;

        // length of 'str'
        int len = str.Length;

        // get frequency of each character of 'str'
        for (int i = 0; i < len; i++) {
            if (str[i] != ' ') {
                freq[str[i] - 'a']++;
            }
        }

        // for each character, where character is obtained by
        // (i + 'a') check whether it is the maximum character
        // so far and accordingly update 'result'
        for (int i = 0; i < 26; i++) {
            if (max < freq[i]) {
                max = freq[i];
                result = (char) (i + 'a');
            }
        }

        // maximum occurring character
        return result;
    }

// Driver Code
    public static void Main() {
        string str = "sample program";
        Console.WriteLine("Maximum occurring character = "
                + getMaxOccurringChar(str));
    }
}

Output

Maximum occurring character = a

complexity Analysis:

• Time Complexity: O(n), where n is the length of the given input string. 
• Auxiliary Space: O(1).

Source: Sabre Interview Experience | Set 2