Lucky Four Codechef Solution

Kostya likes the number 4 much. Of course! This number has such a lot of properties, like:

  • Four is the smallest composite number;
  • It is also the smallest Smith number;
  • The smallest non-cyclic group has four elements;
  • Four is the maximal degree of the equation that can be solved in radicals;
  • There is four-color theorem that states that any map can be colored in no more than four colors in such a way that no two adjacent regions are colored in the same color;
  • Lagrange’s four-square theorem states that every positive integer can be written as the sum of at most four square numbers;
  • Four is the maximum number of dimensions of a real division algebra;
  • In bases 6 and 12, 4 is a 1-automorphic number;
  • And there are a lot more cool stuff about this number!

Impressed by the power of this number, Kostya has begun to look for occurrences of four anywhere. He has a list of T integers, for each of them he wants to calculate the number of occurrences of the digit 4 in the decimal representation. He is too busy now, so please help him.


The first line of input consists of a single integer T, denoting the number of integers in Kostya’s list.

Then, there are T lines, each of them contain a single integer from the list.


Output T lines. Each of these lines should contain the number of occurences of the digit 4 in the respective integer from Kostya’s list.


  • 1 ≤ T ≤ 10^5
  • (Subtask 1): 0 ≤ Numbers from the list ≤ 9 – 33 points.
  • (Subtask 2): 0 ≤ Numbers from the list ≤ 109 – 67 points.






Lucky Four – CodeChef Solution in Python

T = int(input())
for _ in range(T):
  n = int(input())
  count = 0
  while n > 0:
    if n % 10 == 4:
          count += 1
    n = n // 10

Lucky Four – CodeChef Solution in CPP

#include <iostream>
using namespace std;
int main() {
    // * Initializing variables
    int numberOfTestCases, number, count;
    // * Accepting the number of test cases
    // * Executing each test case one by one
    while(numberOfTestCases--) {
        // * Accepting number
        // * Initializing the count to 0 for current test case
        count = 0;
        // * Looping while number is not equal to zero
        while(number != 0) {
            // * Incrementing count if the last digit of number is 4
            if(number%10 == 4) {
            // * Removing the last digit from number
            number = number/10;
        // * Displaying the value of count for current test case

Lucky Four – CodeChef Solution in JAVA

Disclaimer: The above Problem (Lucky Four) is generated by CodeChef but the solution is provided by Chase2learn.This tutorial is only for Educational and Learning purpose.

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