Strings are a very important topic in programming interviews. It's wise to practice some programming problems focused on strings before your interviews. In this article, you'll learn how to find the most frequently occurring character in a string.

Examples to Sympathise the Problem

Example 1: Let the given string be "Makeuseof". The character 'e' occurs 2 times in the given string and all the other characters occur merely one time. Thus, the character 'due east' has the highest frequency in the given string.

Example 2: Let the given string be "She sees cheese". The graphic symbol 'e' occurs 6 times in the given string and all the other characters occur less than 6 times. Thus, the graphic symbol 'e' has the highest frequency in the given cord.

Approach to Detect the Most Frequently Occurring Character in a String

The hashing technique is the most efficient fashion to find the character having the highest frequency in a string. In this technique, the string is traversed and each character of the string is hashed into an array of ASCII characters.

Permit the input string exist "Makeuseof", each grapheme of this string is hashed as following:

frequency['M'] = i

frequency['a] = ane

frequency['g'] = 1

frequency['e'] = 2

frequency['u'] = i

frequency['s'] = 1

frequency['o'] = 1

frequency['f'] = one

The index of the maximum value in the frequency assortment is returned. Here2 is the highest value, therefore 'due east' is returned.

C++ Program to Notice the Graphic symbol With the Highest Frequency

Below is the C++ programme to discover the character with the highest frequency in a string:

                      // C++ programme to find the character            
            // having the highest frequency in a cord            
#include            <iostream>            
#include            <string>            
            #define ASCII_SIZE 256            
using            namespace            std;
                          char              maxFrequencyChar              (cord str)                        
{
            // Array to store frequency of each characters            
            // Initialized the frequency of each graphic symbol as 0            
            int            frequency[ASCII_SIZE] = {0};
            // Finding length of the input string            
            int            lenOfStr = str.length();
            // Initialize maxFrequency variable            
            int            maxFrequency = -i;
            // Initialize maxFrequencyChar variable            
            char            maxFrequencyChar;
            // Traversing and maintaining the            
            // frequency of each characters            
            for            (int            i =            0; i < lenOfStr; i++)
            {
            frequency            [str[i]]++;
            if (maxFrequency            <            frequency[str[i]])
            {
            maxFrequency = frequency[str[i]];
            maxFrequencyChar = str[i];
            }
            }
            render            maxFrequencyChar;
}
            // Commuter Code            
                          int              master              ()                        
{
            string str1 =            "Which witch is which?";
            cout            <            <            "str1: "            <            <            str1            <            <            endl;
            cout            <            <            "The highest frequency character is: "            <            <            maxFrequencyChar(str1)            <            <            endl;
            cord str2 =            "He threw three gratis throws";
            cout            <            <            "str2: "            <            <            str2            <            <            endl;
            cout            <            <            "The highest frequency grapheme is: "            <            <            maxFrequencyChar(str2)            <            <            endl;
            cord str3 =            "Eddie edited information technology";
            cout            <            <            "str3: "            <            <            str3            <            <            endl;
            cout            <            <            "The highest frequency graphic symbol is: "            <            <            maxFrequencyChar(str3)            <            <            endl;
            string str4 =            "Makeuseof";
            cout            <            <            "str4: "            <            <            str4            <            <            endl;
            cout            <            <            "The highest frequency character is: "            <            <            maxFrequencyChar(str4)            <            <            endl;
            cord str5 =            "She sees cheese";
            cout            <            <            "str5: "            <            <            str5            <            <            endl;
            cout            <            <            "The highest frequency character is: "            <            <            maxFrequencyChar(str5)            <            <            endl;
}

Output:

          str1: Which witch is            which?
The highest frequency character            is: h
str2: He threw three complimentary            throws            
The highest frequency character            is: e
str3: Eddie edited it
The highest frequency character            is: d
str4: Makeuseof
The highest frequency character            is: e
str5: She sees cheese
The highest frequency character            is: eastward

Python Program to Find the Graphic symbol With the Highest Frequency

Below is the Python programme to find the grapheme with the highest frequency in a string:

                      # Python programme to detect the character            
            # having the highest frequency in a string            
ASCII_SIZE =            256            
                          def              maxFrequencyChar              (str):            
            # Assortment to shop frequency of each characters            
            # Initialized the frequency of each grapheme as 0            
            frequency = [0] * ASCII_SIZE
            # Initialize maxFrequency variable            
            maxFrequency =            -one            
            # Initialize maxFrequencyChar variable            
            maxFrequencyChar =            ''            
            # Traversing and maintaining the            
            # frequency of each characters            
            for            i            in            str:
            frequency[ord(i)] +=            1            
            for            i            in            str:
            if            maxFrequency < frequency[ord(i)]:
            maxFrequency = frequency[ord(i)]
            maxFrequencyChar = i
            return            maxFrequencyChar
            # Driver Code            
str1 =            "Which witch is which?"            
impress("str1:", str1)
print("The highest frequency character is:", maxFrequencyChar(str1))
str2 =            "He threw 3 free throws"            
print("str2:", str2)
impress("The highest frequency graphic symbol is:", maxFrequencyChar(str2))
str3 =            "Eddie edited it"            
print("str3:", str3)
print("The highest frequency character is:", maxFrequencyChar(str3))
str4 =            "Makeuseof"            
print("str4:", str4)
impress("The highest frequency character is:", maxFrequencyChar(str4))
str5 =            "She sees cheese"            
impress("str5:", str5)
print("The highest frequency character is:", maxFrequencyChar(str5))

Output:

          str1: Which witch is            which?
The highest frequency character            is: h
str2: He threw three free            throws            
The highest frequency character            is: eastward
str3: Eddie edited it
The highest frequency graphic symbol            is: d
str4: Makeuseof
The highest frequency character            is: e
str5: She sees cheese
The highest frequency character            is: e

C Program to Observe the Grapheme With the Highest Frequency

Below is the C program to find the character with the highest frequency in a string:

                      // C program to observe the grapheme            
            // having the highest frequency in a string            
#include            <iostream>            
#include            <cstring>            
            #define ASCII_SIZE 256            
using            namespace            std;
                          char              maxFrequencyChar              (char                *str)                        
{
            // Array to shop frequency of each characters            
            // Initialized the frequency of each graphic symbol equally 0            
            int            frequency[ASCII_SIZE] = {0};
            // Finding length of the input string            
            int            lenOfStr = strlen(str);
            // Initialize maxFrequency variable            
            int            maxFrequency =            0;
            // Initialize maxFrequencyChar variable            
            char            maxFrequencyChar;
            // Traversing and maintaining the            
            // frequency of each characters            
            for            (int            i =            0; i < lenOfStr; i++)
            {
            frequency            [str[i]]++;
            if (maxFrequency            <            frequency[str[i]])
            {
            maxFrequency = frequency[str[i]];
            maxFrequencyChar = str[i];
            }
            }
            return            maxFrequencyChar;
}
            // Driver Code            
                          int              main              ()                        
{
            char            str1[] =            "Which witch is which?";
            printf("str1: %southward", str1);
            printf("The highest frequency character is: %c \⁠due north", maxFrequencyChar(str1));
            char            str2[] =            "He threw three costless throws";
            printf("str2: %southward", str2);
            printf("The highest frequency character is: %c \⁠n", maxFrequencyChar(str2));
            char            str3[] =            "Eddie edited it";
            printf("str3: %s", str3);
            printf("The highest frequency character is: %c \⁠n", maxFrequencyChar(str3));
            char            str4[] =            "Makeuseof";
            printf("str4: %due south", str4);
            printf("The highest frequency graphic symbol is: %c \⁠n", maxFrequencyChar(str4));
            char            str5[] =            "She sees cheese";
            printf("str1: %due south", str5);
            printf("The highest frequency graphic symbol is: %c \⁠n", maxFrequencyChar(str5));
}

Output:

          str1: Which witch is            which?
The highest frequency graphic symbol            is: h
str2: He threw three costless            throws            
The highest frequency grapheme            is: eastward
str3: Eddie edited it
The highest frequency character            is: d
str4: Makeuseof
The highest frequency character            is: e
str5: She sees cheese
The highest frequency grapheme            is: due east

JavaScript Program to Find the Character With the Highest Frequency

Below is the JavaScript program to find the character with the highest frequency in a cord:

                      // JavaScript program to notice the grapheme            
            // having the highest frequency in a string            
            let            ASCII_SIZE =            256;
                          part              maxFrequencyChar(str)            
{
            // Array to store frequency of each characters            
            // Initialized the frequency of each graphic symbol equally 0            
            permit            frequency =            new            Array(ASCII_SIZE);
            for            (let            i =            0; i < ASCII_SIZE; i++)
            {
            frequency[i] = 0;
            }
            // Finding length of the input string            
            let            lenOfStr = str.length;
            for            (permit            i =            0; i < lenOfStr; i++)
            {
            frequency[str[i].charCodeAt(0)] += 1;
            }
            // Initialize maxFrequency variable            
            let            maxFrequency =            -1;
            // Initialize maxFrequencyChar variable            
            permit            maxFrequencyChar =            '';
            // Traversing and maintaining the            
            // frequency of each characters            
            for            (let            i =            0; i < lenOfStr; i++)
            {
            if            (maxFrequency            &lt;            frequency            [str[i]            .charCodeAt(0)])
            {
            maxFrequency = frequency[str[i].charCodeAt(0)];
            maxFrequencyChar = str[i];
            }
            }
            return            maxFrequencyChar;
}
            // Driver Code            
            let            str1 =            "Which witch is which?";
            certificate.write("str1: "            + str1 +            "<br>");
            certificate.write("The highest frequency character is: "            + maxFrequencyChar(str1) +            "<br>")
            let            str2 =            "He threw three free throws";
            document.write("str2: "            + str2 +            "<br>");
            document.write("The highest frequency graphic symbol is: "            + maxFrequencyChar(str2) +            "<br>")
            let            str3 =            "Eddie edited it";
            document.write("str3: "            + str3 +            "<br>");
            certificate.write("The highest frequency character is: "            + maxFrequencyChar(str3) +            "<br>")
            let            str4 =            "Makeuseof";
            document.write("str4: "            + str4 +            "<br>");
            certificate.write("The highest frequency character is: "            + maxFrequencyChar(str4) +            "<br>")
            let            str5 =            "She sees cheese";
            document.write("str5: "            + str5 +            "<br>");
            document.write("The highest frequency character is: "            + maxFrequencyChar(str5) +            "<br>")

Output:

          str1: Which witch is            which?
The highest frequency character            is: h
str2: He threw three free            throws            
The highest frequency graphic symbol            is: east
str3: Eddie edited information technology
The highest frequency character            is: d
str4: Makeuseof
The highest frequency grapheme            is: e
str5: She sees cheese
The highest frequency character            is: e

Analyze the Fourth dimension and Space Complexity

The fourth dimension complexity of themaxFrequencyChar() function is O(due north). The space complexity of themaxFrequencyChar() office is O(one) as a stock-still space (Hash array). Information technology does not depend on the input string size.

Big-O notation gives you a way to calculate how long information technology will accept to run your lawmaking. It's one of the nigh important concepts for the analysis of algorithms. If you lot're a programmer, you must know about Big-O Notation.

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About The Author

Yuvraj Chandra (84 Articles Published)

Yuvraj is a Computer Science undergraduate student at the University of Delhi, India. He's passionate about Total Stack Web Development. When he's not writing, he's exploring the depth of unlike technologies.

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