Write a C Program to count the frequency of each character

Follow the algorithm to write a C program which enables to count the frequency of each character.

Algorithm

Step 1: Define MAX size. Step 2: Declare char and integer variables. Step 3: Read the string from console. Step 4: Find length of the string. Step 5: Initialize frequency of each character to 0. Step 6: Find total number of occurrences of each character. for(i=0; i<length; i++)    i. if(string[i]>='a' && string[i]<='z')    frequency[string[i] - 97]++;    ii. else if(string[i]>='A' && string[i]<='Z')       frequency[string[i] - 65]++; Step 7: Print the frequency of all characters in the string. if(frequency[i] != 0)    printf("'%c' = %d
", (i + 97), frequency[i]);

Example

Given below is the C program to count frequency of each character in a string −

 Live Demo

#include <stdio.h> #include <string.h> #define MAX 100 // Maximum string size int main(){    char string[MAX];    int i, length;    int frequency[20];    /* Input string from user */    printf("enter the string:
 ");    gets(string);    length = strlen(string);    /* Initialize frequency of each character to 0 */    for(i=0; i<20; i++){       frequency[i] = 0;    }    /* Find total number of occurrences of each character */    for(i=0; i<length; i++){       /* If the current character is lowercase alphabet */       if(string[i]>='a' && string[i]<='z'){          frequency[string[i] - 97]++;       }       else if(string[i]>='A' && string[i]<='Z'){          frequency[string[i] - 65]++;       }    }    /* Print the frequency of all characters in the string */    printf("
Frequency of all characters in string: 
");    for(i=0; i<20; i++){       /* If current character exists in given string */       if(frequency[i] != 0){          printf("'%c' = %d
", (i + 97), frequency[i]);       }    }    return 0; }

Output

When the above program is executed, it produces the following result −

enter the string: Tutorials Point Frequency of all characters in string: 'a' = 1 'i' = 2 'l' = 1 'n' = 1 'o' = 2 'p' = 1 'r' = 1 's' = 1 't' = 3