Blue Bridge Cup 31 day sprint Day8

Magic formula

link : Magic formula .

The idea is simple , It's just a combination of different numbers that list all the digits （4 individual for loop ）, Then use the hash table to check each number of the duplicate result , Re statistics

But I stepped on the pit , Special attention ： The number beginning with cannot be 0！！！

Code ：

public class  Magic formula  {
    

	public static void main(String[] args) {
    
		// TODO Auto-generated method stub
		int count1 = 0;
		int count2=0;
		int n=0;
		// All four numbers are different （i The number that starts with cannot be 0）
		for(int i =1;i<=9;i++) {
    
			for(int j =0;j<=9;j++) {
    
				if(j==i)
					j++;
				if(j>9)
					break;
				for(int k =0;k<=9;k++) {
    
					while(k==i||k==j)
						k++;
					if(k>9)
						break;
					for(int t =0;t<=9;t++) {
    
						while(t==i||t==j||t==k)
							t++;
						if(t>9)
							break;
						//1 digit *3 digit 
						if(j!=0) {
    
							n=i*(100*j+10*k+t);
						    if(n>1000&&n<9999&&isDifferent(n,i,j,k,t)) 
						    	count1++;
						}
						
						//2 digit *2 digit 
						if(k!=0) {
    
							n = (i*10+j)*(k*10+t);
						    if(n>1000&&n<9999&&isDifferent(n,i,j,k,t)) 
					    	count2++;
						}
						
					}
				}
			}
		}
		//count2 except 2 It's for weight removal 
		System.out.println(count1+count2/2);

	}
	
	public static boolean isDifferent(int n,int i ,int j,int k,int t) {
    
		int[] hash = new int[10];
		hash[n/1000]++;
		hash[n%1000/100]++;
		hash[n%100/10]++;
		hash[n%10]++;
		if(hash[i]==1&&hash[j]==1&&hash[k]==1&&hash[t]==1)
			return true;
		return false;
	}

}

Contraction summation

link : Contraction summation .


Because the input will not exceed 1000 position , Not more than 9999, It's safe to use int Calculation . Put... Directly String Turn into char Just calculate the array

Code ：

import java.util.*;

public class  Contraction summation  {
    

	public static void main(String[] args) {
    
		// TODO Auto-generated method stub
		Scanner sc = new Scanner(System.in);
		while(sc.hasNext()) {
    
			String s = sc.nextLine();
		int n=0;	
		for(char c : s.toCharArray()) {
    
			n+=c-'0';
		}
		
		while(n>=10) {
    
			int num=0;
			char[] chars =Integer.toString(n).toCharArray();
		    for(int i=0;i<chars.length;i++) {
    
		    	num+=chars[i]-'0';
		    }
		    n=num;
		}
		System.out.println(Integer.toString(n));
		}
		
	}

}

Building blocks competition

link : Building blocks competition .