# Form a number using corner digits of powers

Given two integers N and X. Make a number in such a way that the number contains the first and last digit occurring in .

Examples :

Input : N = 10, X = 5
Output : 1010101010
Explanation :
10^1 = 10
10^2 = 100
10^3 = 1000
10^4 = 10000
10^5 = 100000
Take First and Last Digit of each Power to
get required number.

Input : N = 19, X = 4
Output : 19316911
Explanation :
19^1 = 19
19^2 = 361
19^3 = 6859
19^4 = 130321
Take First and Last Digit of each Power to get required number.

# Recommended: Please solve it on “PRACTICE“first, before moving on to the solution.

Approach :
1. Calculate all Powers of N from 1 to X one by one.
2. Store the Output in power[] array.
3. Store power[0] i.e, last_digit and power[power_size – 1] i.e, unit_digit from power[] array to result[] array.
4. Print the result[] Array.

Below is the implementation of the above approach :

## C++

 // C++ program to find number formed by // corner digits of powers. #include using namespace std;    // Find next power by multiplying N with // current power void nextPower(int N, vector &power) {     int carry = 0;        for (int i=0 ; i < power.size(); i++)     {         int prod = (power[i] * N) + carry ;            // Store digits of Power one by one.         power[i] = prod % 10 ;            // Calculate carry.         carry = prod / 10 ;     }        while (carry)     {         // Store carry in Power array.         power.push_back(carry % 10);         carry = carry / 10 ;     } }    // Prints number formed by corner digits of // powers of N. void printPowerNumber(int X, int N) {     // Storing N raised to power 0     vector power;     power.push_back(1);        // Initializing empty result     vector res;        // One by one compute next powers and     // add their corner digits.     for (int i=1; i<=X; i++)     {         // Call Fucntion that store power         // in Power array.         nextPower(N, power) ;            // Store unit and last digits of         // power in res.         res.push_back(power.back());         res.push_back(power.front());     }        for (int i=0 ; i < res.size(); i++)         cout << res[i] ; }    // Driver Code int main() {     int N = 19 , X = 4;     printPowerNumber(X, N);     return 0 ; }

## Java

 // Java program to find number formed by // corner digits of powers. import java.io.*; import java.util.*;     public class GFG {            static List power = new ArrayList();     // Find next power by multiplying N      // with current power     static void nextPower(Integer N)     {         Integer carry = 0;                 for (int i = 0; i < power.size(); i++)         {             Integer prod = (power.get(i) * N) + carry ;                     // Store digits of Power one by one.             power.set(i,prod % 10);                     // Calculate carry.             carry = prod / 10 ;         }                 while (carry >= 1)         {             // Store carry in Power array.             power.add(carry % 10);             carry = carry / 10 ;         }     }             // Prints number formed by corner digits of     // powers of N.     static void printPowerNumber(int X, int N)     {                     // Storing N raised to power 0         power.add(1);                 // Initializing empty result         List res = new ArrayList();                 // One by one compute next powers and         // add their corner digits.         for (int i = 1; i <= X; i++)         {             // Call Fucntion that store power             // in Power array.             nextPower(N) ;                     // Store unit and last digits of             // power in res.             res.add(power.get(power.size() - 1));             res.add(power.get(0));         }                 for (int i = 0 ; i < res.size(); i++)             System.out.print(res.get(i)) ;     }             // Driver Code     public static void main(String args[])     {         Integer N = 19 , X = 4;         printPowerNumber(X, N);     } }     // This code is contributed by Manish Shaw // (manishshaw1)

## Python3

 # Python3 program to find  # number formed by  # corner digits of powers.     # Storing N raised to power 0 power = []    # Find next power by multiplying  # N with current power def nextPower(N) :     global power     carry = 0          for i in range(0, len(power)) :         prod = (power[i] * N) + carry               # Store digits of          # Power one by one.         power[i] = prod % 10               # Calculate carry.         carry = (int)(prod / 10)           while (carry) :            # Store carry in Power array.         power.append(carry % 10)         carry = (int)(carry / 10)       # Prints number formed by corner  # digits of powers of N. def printPowerNumber(X, N) :     global power     power.append(1)          # Initializing empty result     res = []          # One by one compute next powers      # and add their corner digits.     for i in range(1, X+1) :            # Call Fucntion that store          # power in Power array.         nextPower(N)               # Store unit and last          # digits of power in res.         res.append(power[-1])         res.append(power[0])          for i in range(0, len(res)) :         print (res[i], end="")       # Driver Code N = 19  X = 4 printPowerNumber(X, N)      # This code is contributed by  # Manish Shaw(manishshaw1)

## C#

 // C# program to find number formed by // corner digits of powers. using System; using System.Collections.Generic; using System.Linq; using System.Collections;    class GFG {            // Find next power by multiplying N      // with current power     static void nextPower(int N, ref List power)     {         int carry = 0;                for (int i = 0; i < power.Count; i++)         {             int prod = (power[i] * N) + carry ;                    // Store digits of Power one by one.             power[i] = prod % 10 ;                    // Calculate carry.             carry = prod / 10 ;         }                while (carry >= 1)         {             // Store carry in Power array.             power.Add(carry % 10);             carry = carry / 10 ;         }     }            // Prints number formed by corner digits of     // powers of N.     static void printPowerNumber(int X, int N)     {                    // Storing N raised to power 0         List power = new List();         power.Add(1);                // Initializing empty result         List res = new List();                // One by one compute next powers and         // add their corner digits.         for (int i = 1; i <= X; i++)         {             // Call Fucntion that store power             // in Power array.             nextPower(N, ref power) ;                    // Store unit and last digits of             // power in res.             res.Add(power.Last());             res.Add(power.First());         }                for (int i = 0 ; i < res.Count; i++)             Console.Write(res[i]) ;     }            // Driver Code     public static void Main()     {         int N = 19 , X = 4;         printPowerNumber(X, N);     } }    // This code is contributed by Manish Shaw // (manishshaw1)

## PHP



Output :

19316911

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