23届秋招阿里笔试算法题

import java.util.Scanner;

//23届秋招阿里笔试第一题：二进制求解(100%)
public class Main1 {

	public static void f1(int n) {
		String str= Integer.toString(n, 2);
		for (int i = 0; i < str.length(); i++) {
			if(str.charAt(i)=='1') {
				System.out.print((char)('a'+str.length()-1-i));
			}
		}
	}
	
	public static void main(String[] args) {
		Scanner sc=new Scanner(System.in);
		f1(sc.nextInt());
	}

}

import java.util.Scanner;

//23届秋招阿里笔试第二题：树技巧求解(0%)
public class Main2 {

	public static void f2(int[] arr,int[][] help) {
		int sum=0;
		for (int i = 0; i < arr.length; i++) {
			for (int j = 0; j < help.length; j++) {
				if(help[1][j]==i+1) {
					sum+=(i+1-help[0][j]);
				}
			}
		}
		System.out.println(sum);
	}
	
	public static void main(String[] args) {
		Scanner sc=new Scanner(System.in);
		int n=sc.nextInt();
		int[] arr=new int[n];
		int[][] help=new int[2][n-1];
        for (int i = 0; i < n-1; i++) {
        	help[0][i]=sc.nextInt();
            help[1][i]=sc.nextInt();
		}
        f2(arr, help);
	}

}

import java.util.Scanner;

//23届秋招阿里笔试第三题：动规求解(20%)
public class Main3 {

	public static void f3(String str) {
		Long[] arr=new Long[str.length()];
		arr[0]=1L;
		for (int i = 1; i < arr.length; i++) {
			arr[i]=1+arr[i-1];
			for (int j = i-1; j >=0; j--) {
				if(check(str.substring(j, i+1))) {
					arr[i]++;
				}
			}
		}
		System.out.println(arr[str.length()-1]);
	}
	
	public static boolean check(String str) {
		int[] help=new int[26];
		for (int i = 0; i < str.length(); i++) {
			help[str.charAt(i)-'a']++;
		}
		boolean flag=false;
		for (int i = 0; i < help.length; i++) {
			if(help[i]%2!=0) {
				if(flag) {
					return false;
				}
				flag=true;
			}
		}
		return flag;
	}
	
	public static void main(String[] args) {
		Scanner sc=new Scanner(System.in);
		f3(sc.next());
	}

}