CPP Program Find the Cube Free Number – Number Theory

  • A cube free number is a number whose none of the divisors is a cube number (A cube number is a cube of an integer like 8 (2 * 2 * 2), 27 (3 * 3 * 3) ). So cube free numbers are 1, 2, 3, 4, 5, 6, 7, 9, 10, 11, 12, 13, 14, 15, 17, 18 etc (we will consider 1 as cube free). 8, 16, 24, 27, 32, etc are not cube-free numbers. So the position of 1 among the cube-free numbers is 1, the position of 2 is 2, 3 is 3 and the position of 10 is 9.
  • Given a positive number you have to say if it’s a cube-free number and if yes then tell its position among cube-free numbers.

Input:

The first line of the test case will be the number of test cases T (1 <= T <= 100000). Then T lines follow. On each line you will find a integer number n (1 <= n <= 1000000).

Output:

For each input line, print a line containing “Case I: ”, where I am the test case number. Then if it is not a cube-free number then print “Not Cube Free”. Otherwise, print its position among the cube-free numbers.

Sample Input:

10
1
2
3
4
5
6
7
8
9
10

Sample Output:

Case 1: 1
Case 2: 2
Case 3: 3
Case 4: 4
Case 5: 5
Case 6: 6
Case 7: 7
Case 8: Not Cube Free
Case 9: 8
Case 10: 9

Code:

#include<iostream> using namespace std; void Sieve_Array_Filler(int*arr) { for(int i=0; i<1000001; i++) { arr[i]=0; } arr[1]=1; for(int i=2; i<=100; i++) { int current_cubic_number=i*i*i; for(int j=1; current_cubic_number*j<1000001;j++) { arr[current_cubic_number*j]=-1; } } int k=1; for(int i=1; i<=1000000; i++) { if(arr[i]!=-1) { arr[i]=k; k++; } } } int main() { int t; cin>>t; int *arr=new int [1000001]; Sieve_Array_Filler(arr); for(int test_case=1; test_case<=t; test_case++) { int n; cin>>n; if(arr[n]!=-1) { cout<<"Case "<<test_case<<": "<<arr[n]<<endl; } else { cout<<"Case "<<test_case<<": "<<"Not Cube Free"<<endl; } } }
Code language: C++ (cpp)

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