Representation of a number in powers of other
Last Updated :
25 Aug, 2022
Given two numbers w and m, we need to determine whether it is possible to represent m in terms of powers of w. The powers of number w can be added or subtracted to obtain m and each powers of w can be used only once .
Examples:
Input : 3 7
Output : Yes
As 7 = 9 - 3 + 1 (3^2 - 3^1 + 3^0 )
so it is possible .
Input : 100 50
Output : No
As 50 is less than 100 so we can never
represent it in the powers of 100 .
Here we have to represent m in terms of powers of w used only once so it can be shown through the following equation .
c0 + c1*w^1 + c2*w^2 + ... = m ------ (Equation 1)
Where each c0, c1, c2 ... are either -1 (for subtracting that power of w ), 0 (not using that power of w ), 1 (for adding that power of w ) .
=> c1*w^1 + c2*w^2 + ... = m - c0
=> w(c1 + c2*w^1 + c3*w^2 + ... ) = m - c0
=> c1 + c2*w^1 + c3*w^2 + ... = (m - c0)/w ------ (Equation 2)
Now, notice equation 1 and equation 2 -- we are trying to solve the same problem all over again. So we have to recurse till m > 0 . For such a solution to exist (m — ci) must be a multiple of w, where ci is the coefficient of the equation . The ci can be -1, 0, 1 . So we have to check for all three possibilities ( ( m - 1 ) % w == 0), ( ( m + 1 ) % w == 0) and ( m % w == 0) . If it is not, then there will not be any solution.
C++
// CPP program to check if m can be represented
// as powers of w.
#include <bits/stdc++.h>
using namespace std;
bool asPowerSum(int w, int m)
{
while (m) {
if ((m - 1) % w == 0)
m = (m - 1) / w;
else if ((m + 1) % w == 0)
m = (m + 1) / w;
else if (m % w == 0)
m = m / w;
else
break; // None of 3 worked.
}
// If m is not zero means, it can't be
// represented in terms of powers of w.
return (m == 0);
}
// Driver code
int main()
{
int w = 3, m = 7;
if (asPowerSum(w, m))
cout << "Yes" << endl;
else
cout << "No" << endl;
return 0;
}
Java
// Java program to check if m can
// be represented as powers of w.
class GFG
{
static boolean asPowerSum(int w, int m)
{
while (m > 0)
{
if ((m - 1) % w == 0)
m = (m - 1) / w;
else if ((m + 1) % w == 0)
m = (m + 1) / w;
else if (m % w == 0)
m = m / w;
else
break; // None of 3 worked.
}
// If m is not zero means, it can't be
// represented in terms of powers of w.
return (m == 0);
}
// Driver function
public static void main (String[] args)
{
int w = 3, m = 7;
if (asPowerSum(w, m))
System.out.println("Yes");
else
System.out.println("No");
}
}
// This code is contributed by Anant Agarwal.
Python3
# Python3 program to check if m can
# be represented as powers of w.
def asPowerSum(w, m):
while (m > 0):
if ((m - 1) % w == 0):
m = (m - 1) / w;
elif ((m + 1) % w == 0):
m = (m + 1) / w;
elif (m % w == 0):
m = m / w;
else:
break; # None of 3 worked.
# If m is not zero means, it can't be
# represented in terms of powers of w.
return (m == 0);
# Driver code
w = 3;
m = 7;
if (asPowerSum(w, m)):
print("Yes");
else:
print("No");
# This code is contributed by mits
C#
// C# program to check if
// m can be represented
// as powers of w.
using System;
class GFG
{
static bool asPowerSum(int w,
int m)
{
while (m > 0)
{
if ((m - 1) % w == 0)
m = (m - 1) / w;
else if ((m + 1) % w == 0)
m = (m + 1) / w;
else if (m % w == 0)
m = m / w;
else
break; // None of 3 worked.
}
// If m is not zero means,
// it can't be represented
// in terms of powers of w.
return (m == 0);
}
// Driver Code
static public void Main ()
{
int w = 3, m = 7;
if (asPowerSum(w, m))
Console.WriteLine("Yes");
else
Console.WriteLine("No");
}
}
// This code is contributed
// by akt_mit.
PHP
<?php
// PHP program to check if m can
// be represented as powers of w.
function asPowerSum($w, $m)
{
while ($m)
{
if (($m - 1) % $w == 0)
$m = ($m - 1) / $w;
else if (($m + 1) % $w == 0)
$m = ($m + 1) / $w;
else if ($m % $w == 0)
$m = $m / $w;
else
break; // None of 3 worked.
}
// If m is not zero means, it can't be
// represented in terms of powers of w.
return ($m == 0);
}
// Driver code
$w = 3;
$m = 7;
if (asPowerSum($w, $m))
echo "Yes\n";
else
echo "No\n";
// This code is contributed by mits
?>
JavaScript
<script>
// Javascript program to check if m can
// be represented as powers of w.
function asPowerSum(w, m)
{
while (m > 0)
{
if ((m - 1) % w == 0)
m = (m - 1) / w;
else if ((m + 1) % w == 0)
m = (m + 1) / w;
else if (m % w == 0)
m = m / w;
else
break; // None of 3 worked.
}
// If m is not zero means, it can't be
// represented in terms of powers of w.
return (m == 0);
}
// Driver code
let w = 3, m = 7;
if (asPowerSum(w, m))
document.write("Yes");
else
document.write("No");
// This code is contributed by sanjoy_62.
</script>
Output:
Yes
Time complexity: O(m)
Auxiliary space: O(1)
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