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Repdigit Numbers
  • Last Updated : 08 Jul, 2020

Repdigit Number is a number N which has all the digits in its representation in base B equal.

Some of the Repdigit number are:

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 22, 33, 44, 55….

Check if N is an Repdigit number

Given a number N, the task is to check if N is an Repdigit Number in Base B or not. If N is a Repdigit Number in Base B then print “Yes” else print “No”.

Examples:



Input: N = 2000, B = 7
Output: Yes
Explanation:
2000 in base 7 is 5555 which has all digits equal.

Input: N = 112, B = 10
Output: No

Approach:

  • One by one find all the digits of N in base B.
  • Compare every digit with its previous digit.
  • If any digit is not equal to the previous digit then return false.
  • Otherwise return true.

Below is the implementation of the above approach:

C++

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// C++ implementation to check 
// if a number is Repdigit
  
#include <iostream>
using namespace std;
  
// Function to check if a number 
// is a Repdigit number
bool isRepdigit(int num, int b)
{
    // To store previous digit (Assigning
    // initial value which is less than any
    // digit)
    int prev = -1;
  
    // Traverse all digits from right to
    // left and check if any digit is
    // smaller than previous.
    while (num) {
        int digit = num % b;
        num /= b;
        if (prev != -1 && digit != prev)
            return false;
        prev = digit;
    }
  
    return true;
}
  
// Driver code
int main()
{
    int num = 2000, base = 7;
    isRepdigit(num, base) ? cout << "Yes"
                          : cout << "No";
    return 0;
}

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Java

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// Java implementation to check 
// if a number is Repdigit
class GFG{
  
// Function to check if a number 
// is a Repdigit number
static boolean isRepdigit(int num, int b)
{
    // To store previous digit (Assigning
    // initial value which is less than any
    // digit)
    int prev = -1;
  
    // Traverse all digits from right to
    // left and check if any digit is
    // smaller than previous.
    while (num != 0)
    {
        int digit = num % b;
        num /= b;
        if (prev != -1 && digit != prev)
            return false;
        prev = digit;
    }
    return true;
}
  
// Driver code
public static void main(String args[])
{
    int num = 2000, base1 = 7;
    if(isRepdigit(num, base1))
    {
        System.out.print("Yes");
    
    else
    {
        System.out.print("No");
    }
}
}
  
// This code is contributed by Code_Mech

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Python3

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# Python3 implementation to check 
# if a number is Repdigit 
  
# Function to check if a number 
# is a Repdigit number 
def isRepdigit(num, b) :
      
    # To store previous digit (Assigning
    # initial value which is less than any
    # digit)
    prev = -1
  
    # Traverse all digits from right to
    # left and check if any digit is
    # smaller than previous.
    while (num) :
        digit = num % b
        num //= b
        if (prev != -1 and digit != prev) :
            return False
        prev = digit
    return True
  
# Driver code 
num = 2000
base = 7
if(isRepdigit(num, base)):
    print("Yes")
else:
    print("No"
  
# This code is contributed by Vishal Maurya.

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C#

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// C# implementation to check 
// if a number is Repdigit
using System;
class GFG{
  
// Function to check if a number 
// is a Repdigit number
static bool isRepdigit(int num, int b)
{
    // To store previous digit (Assigning
    // initial value which is less than any
    // digit)
    int prev = -1;
  
    // Traverse all digits from right to
    // left and check if any digit is
    // smaller than previous.
    while (num != 0)
    {
        int digit = num % b;
        num /= b;
        if (prev != -1 && digit != prev)
            return false;
        prev = digit;
    }
    return true;
}
  
// Driver code
public static void Main()
{
    int num = 2000, base1 = 7;
    if(isRepdigit(num, base1))
    {
        Console.Write("Yes");
    
    else
    {
        Console.Write("No");
    }
}
}
  
// This code is contributed by Code_Mech

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Output:

Yes

Time Complexity: O(n)
Reference: http://www.numbersaplenty.com/set/repdigit/

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