How to Create a Dynamic Array of Strings in C?

C program to find the frequency of characters in a string

Last Updated : 01 Jun, 2023

Given a string S containing lowercase English characters, the task is to find the frequency of all the characters in the string.

Examples

Input: S="geeksforgeeks"
Output:
e - 4
f - 1
g - 2
k - 2
o - 1
r - 1
s - 2

Input: S="gfg"
Output:
f - 1
g - 2

Approach

Follow the steps to solve the problem:

Initialize an array freq[] to store the frequency of each alphabet in the given string. The 0^th index stores the frequency of the character 'a', the 1^stindex stores the frequency of the character 'b', and so on.
Iterate over the given string S and increment the frequency of each character encountered by 1, by performing freq[S[i] - 'a'] += 1. If S[i] = 'a', then S[i] - 'a' is equal to 0, therefore the frequency of 'a' is incremented in the array.
After complete traversal of the string, print the frequency of all the characters in the string by traversing the array freq[].

Below is the implementation of the above approach:

C

// C program to find the frequency 
// of characters in a string
#include <stdio.h>
#include <string.h>

// Function to print the frequencies
// of each character of the string
void printFrequency(int freq[])
{
    for (int i = 0; i < 26; i++) 
    {
        // If frequency of the
        // alphabet is non-zero
        if (freq[i] != 0) 
        {
            // Print the character and
            // its respective frequency
            printf("%c - %d\n",
                   i + 'a', freq[i]);
        }
    }
}

// Function to calculate the frequencies
// of each character of the string
void findFrequncy(char S[])
{
    int i = 0;

    // Stores the frequencies
    // of each character
    int freq[26] = { 0 };

    // Traverse over the string
    while (S[i] != '\0') {

        // Increment the count of
        // each character by 1
        freq[S[i] - 'a']++;

        // Increment the index
        i++;
    }

    // Function call to print
    // the frequencies
    printFrequency(freq);
}

// Driver Code
int main()
{
    char S[100] = "geeksforgeeks";
    findFrequncy(S);
}

Output:

e - 4
f - 1
g - 2
k - 2
o - 1
r - 1
s - 2

Complexity of the above method

Time Complexity: O(N)

Auxiliary Space: O(26)

How to Create a Dynamic Array of Strings in C?

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