Count number of digits after decimal on dividing a number

We are given two numbers A and B. We need to calculate the number of digits after decimal. If in case the numbers are irrational then print “INF”.

Examples:

Input  : x = 5, y = 3
Output : INF
5/3 = 1.666....

Input :  x = 3, y = 6
Output : 1
3/6 = 0.5



The idea is simple we follow school division and keep track of remainders while dividing one by one. If remainder becomes 0, we return count of digits seen after decimal. If remainder repeats, we return INF.

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// CPP program to count digits after dot when a
// number is divided by another.
#include <bits/stdc++.h>
using namespace std;
  
int count(int x, int y)
{
    int ans = 0;  // Initialize result
      
    unordered_map<int, int> m;
      
    // calculating remainder
    while (x % y != 0) {
  
        x = x % y;
  
        ans++;
  
        // if this remainder appeared before then 
        // the numbers are irrational and would not
        // converge to a solution the digits after
        // decimal will be infinite
        if (m.find(x) != m.end()) 
            return -1;
  
        m[x] = 1;
        x = x * 10;
    }
    return ans;
}
  
// Driver code
int main()
{
    int res = count(1, 2);
    (res == -1)? cout << "INF" : cout << res;
  
    cout << endl;
    res = count(5, 3);
    (res == -1)? cout << "INF" : cout << res;
  
    cout << endl;
    res = count(3, 5);
    (res == -1)? cout << "INF" : cout << res;
    return 0;
}

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Output:

1
INF
1

This article is contributed by Rahul Chawla. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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