CODEWITHSUNDEEP
c++arraysstringloops
Ashwitha Banoth
Ashwitha Banoth

Reputation: 27

frequency of a digit in an integer in c++

I have been given some integers and I have to count the frequency of a specific digit in the number. example input:

5
447474
228
6664
40
81

The first number says number of integers in the list. I am finding frequency of 4 in this case. I tried to change the integer to an array, but it is not working.


#include<iostream>
#include<cmath>
#include<vector>

using namespace std;

int main() {
    
    int n;
    cin>>n;
    
    for (int i=0; i<n; i++)
    {
       int x;
       cin>>x;
       int frequency=0;
       int t=log10(x);
       int arr[t];
       for (i=t; i>0; i--)
       {
          arr[i]=x%10;
          x=x/10;
       }
       for(int i=0; i<t; i++)
       {
           if(arr[i]==4)
           {
               frequency++;
           }
           
       }
       
     std::cout << frequency << std::endl;
        
    }
    return 0;
}

Upvotes: 0

Views: 742

Answers (2)

463035818_is_not_an_ai
463035818_is_not_an_ai

Reputation: 122724

Your code uses VLAs which are not standard C++. See Why aren't variable-length arrays part of the C++ standard?.

log10(x) is not the number of digits. For example log10(1234) == 3.09131516 but it is 4 digits. Also you are accessing the array out of bounds in the first iteration of the loop: arr[t]. Valid indices in an array of size t are 0,1,2,...,t-1. Trying to access arr[t] is undefined behavior.

Actually you dont need any array. Instead of storing the digits in an array you can immediately check whether it is a 4 and count.

Even simpler would be to read the user input as a std::string:

#include <string>
#include <algorithm>
#include <iostream>

int main() {
    std::string input;
    std::cin >> input;
    std::cout << std::count(input.begin(),input.end(),'4');
}

Perhaps you should add some checks to verify that the user input is actually a valid number. However, also when reading an int you should validate the input.

Upvotes: 0

RaffleBuffle
RaffleBuffle

Reputation: 5455

No need to create an array, or to determine the number of digits. Just loop until the number reaches zero.

int digitCount(int n, int d) {
    if(n < 0) n = -n;
    int count = 0;
    for(; n != 0; n /= 10)
        if(n % 10 == d) count++;
    return count;
}

Test:

cout << digitCount(447474, 4) << endl;
cout << digitCount(-447474, 4) << endl;

Output:

4
4

Upvotes: 2

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