count number of times a character appears in an array? - c++

Question

i've been thinking for a long time and havent got anywhere with the program. i dont know where to begin. The assignment requires use of single function main and only iostream library to be used.
the task is to Declare a char array of 10 elements. Take input from user. Determine if array contains any values more than 1 times . do not show the characters that appears 1 time only.
Sample output:
a 2
b 4
..
a an b are characters. and 2 and 4 represents number of times they appear in the array B.
i tried to use nested loop to compare a character with all the character in array and incrementing a counter each time similer character id sound but unexpected results are occuring.
Here is the code
#include <iostream>
using namespace std;
void main()
{
char ara[10];
int counter=0;
cout<<"Enter 10 characters in an array\n";
for ( int a=0; a<10; a++)
cin>>ara[a];
for(int i=0; i<10; i++)
{
for(int j=i+1; j<10; j++)
{
if(ara[i] == ara[j])
{
counter++;
cout<<ara[i]<<"\t"<<counter<<endl;
}
}
}
}

Answer 1

Algorithm 2: std::map
Declare / define the container:
std::map<char, unsigned int> frequency;
Open the file
read a letter.
find the letter: frequency.find(letter)
If letter exists, increment the frequency: frequency[letter]++;
If letter no exists, insert into frequency: frequency[letter] = 1;
After all letters processed, iterate through the map displaying the letter and its frequency.

Answer 2

Here's one possible way you can solve this. I'm not giving you full code; it's considered bad to just give full implementations for other people's homework.
First, fill a new array with only unique characters. For example, if the input was:
abacdadeff
The new array should only have:
abcdef
That is, every character should appear only once in it. Do not forget to \0-terminate it, so that you can tell where it ends (since it can have a length smaller than 10).
Then create a new array of int (or unsigned, since you can't have negative occurrences) values that holds the frequency of occurence of every character from the unique array in the original input array. Every value should be initially 1. You can achieve this with a declaration like:
unsigned freq[10] = { 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 };
Now, iterate over the unique array and every time you find the current character in the original input array, increment the corresponding element of the frequencies array. So at the end, for the above input, you would have:
a b c d e f (unique array)
3 1 1 2 1 2 (frequencies array)
And you're done. You can now tell how many times each characters appears in the input.

Answer 3

Here, I'll tell you what you should do and you code it yourself:
include headers ( stdio libs )
define main ( entry point for your app )
declare input array A[amount_of_chars_in_your_input]
write output requesting user to input
collect input
now the main part:
declare another array of unsigned shorts B[]
declare counter int i = 0
declare counter int j = 0
loop through the array A[] ( in other words i < sizeof ( A ); or a[i] != '\0' )
now loop as much as there is different letters in the array A
store the amount of letters in the B[]
print it out
Now there are some tricks applying this but you can handle it

Answer 4

Try this:
unsigned int frequency[26] = {0};
char letters[10];
Algorithm:
Open file / read a letter.
Search for the letters array for the new letter.
If the new letter exists: increment the frequency slot for that
letter: frequency[toupper(new_letter) - 'A']++;
If the new letter is missing, add to array and set frequency to 1.
After all letters are processed, print out the frequency array:
`cout << 'A' + index << ": " << frequency[index] << endl;