laba1.java

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.function.Supplier;
import java.util.stream.Stream;
import java.awt.font.NumericShaper.Range;
import java.util.*;

public final class Main {
	
	public static int gcd(int a, int b){
		if(b == 0) return a;
		return gcd(b, a%b);
	}
	
	public static int getDigitSum(int x){
		int res = 0;
		for(int n = 0; n < Math.log10(x); n++){
			int p0 = (int)Math.pow(10, n);
			int p1 = (int)Math.pow(10, n+1);
			res += ((x % p1)  - (x % p0)) / p0;
		}
		return res;
	}
	
	public static boolean fermatTest(int n){
		Random R = new Random();
		int a = R.nextInt();
		while(a % n == 0){
			a = R.nextInt();
		}		
		return Math.pow(a, n-1) == 1 % n;
	}
	
	public static boolean isPrime(int x) {
		if(x == 1) return false;
		if(x == 2) return true;
		if (x % 2 == 0)
			return false;
		for (int d = 3; d <= (int) Math.sqrt(x); d++){
			if (x % d == 0) return false;
		}			
	    return true;
	}
	
	public static int randRange(int a, int b){
		return a + (int)(Math.random() * ((b - a) + 1));
		
	}
	
	public static int sfact(int n){
		int r = 1;
		for(int i=2; i<=n; i++){
			r *= i;
		}
		return r;
	}
	
	public static int[] memo = new int[1000000];
	public static int fact(int n){
		if(n == 1){
			return 1;
		}
		if(memo[n-1] != 0){
			return memo[n-1];
		}
		int res = 1;
		if(n > 0){
			res = n * fact(n-1);
		}
		memo[n-1] = res;
		return res;
	}
	
	public static int factSeq(int n){
		int r = 0;
		for(int s = 1, i=1; i<=n; i++, s*=(-1)){
			r += s*fact(i);
		}
		return r;
	}
	
	
	
	public static boolean isHappy2(int n){
		int nd = (int)Math.ceil(Math.log10(n))/2;
		int rho = (int)Math.pow(10, nd);
		
		int a = n / rho;
		int b = n % rho;
		return getDigitSum(a) == getDigitSum(b);
	}
	
	public static boolean isHappy3(int n){
		int nd = (int)Math.ceil(Math.log10(n))/2;
		int rho = (int)Math.pow(10, nd);
		
		int a = n / (rho*10);
		int b = n % rho;
		return getDigitSum(a) == getDigitSum(b);
	}
	
	public static void showHappy(int n){
		if(n <= 1) return;
		if(n%2 == 0){
			for(int i = (int)Math.pow(10, n-1)+1; 
					i< (int)Math.pow(10, n) - 1; 
					i++){
				if(isHappy2(i)){
					System.out.println(i);
				}
			}
		}
		else{
			for(int i = (int)Math.pow(10, n-1)+1; 
					i< (int)Math.pow(10, n) - 1; 
					i++){
				if(isHappy3(i)){
					System.out.println(i);
				}
			}
		}
	}
	
	
	public static int[] fibArray(int n){
		int[] R = new int[n+1];
		R[0] = 1;
		R[1] = 1;
		for(int i = 2; i <= n; i++){
			R[i] = R[i-1] + R[i-2];
		}
		
		for(int i=0;i<n;i++){
			System.out.println(R[i]);
		}
		return R;
	}
	
	public static int[] primeArray(int n){
		int[] R = new int[n];
		int i = 0;
		int curr = 0;
		while(i != n-1){
			if(isPrime(curr)){
				R[i] = curr;
				System.out.println(curr);
				i++;
			}
			curr++;
		}
		
		return R;
	}
	
	public static char opp(char c){
		if(c == 'B') return 'A';
		return 'B';
	}
	
	public static char[][] chessArray(int n, int m){
		char[][] R = new char[n][m];
		//will be switched to opposite
		char c = 'B';
		for(int i = 0; i<n; i++){
			for(int j = 0; j < m; j++){
				c = opp(c);
				R[i][j] = c;
				System.out.print(c);
			}
			c = opp(c);
			System.out.print('\n');
		}
		
		
		return R;
	}
	
	
	public static void main(String[] args) {
		chessArray(10,20);
		//System.out.println(getDigitSum(123456));
		System.out.println("DONE");

	}
	
	
	private static void lol(){
		Stream<Integer> list = 
				new ArrayList<>(
				Arrays.asList(
				 1
				,2
				,3
				,13
				,20
				)).stream();
		//Supplier<Stream<Integer>> listSource = () -> Stream.of(list);

		
		Integer res = list
			.filter((Integer i) -> i < 10)
			.map((Integer i) -> i*i)
			.reduce(0,((Integer a, Integer b) -> a + b));
		list.forEach((Integer i) -> System.out.println(i));
		System.out.println(res);
	}
	

}