P01 世纪末的星期

package Code2013;

import java.util.Calendar;

/**
 * 
 * 世纪末的星期
 * @author vccyb
 *
 */
public class P001 {
	

	
	 
	public static void main(String[] args) {
		Calendar calendar = Calendar.getInstance();
		for(int year=1999;year<10000;year+=100){
			//一个世纪一个世纪的去翻|
			calendar.set(Calendar.YEAR, year);
			calendar.set(Calendar.MONTH,11);  //11表示设置的是12月
			calendar.set(Calendar.DAY_OF_MONTH, 31);
			System.out.println(year+" "+calendar.get(Calendar.DAY_OF_WEEK));
			if(calendar.get(Calendar.DAY_OF_WEEK)==1){
				System.out.println(year);
				break;
			}
		}
	}
}

1999 6
2099 5
2199 3
2299 1
2299

所以答案就是 2299

java组中用日期api，calendar比较多

P02 振兴中华

只能往右走和往下走

package Code2013;
/**
 * 
 * 
 * 深度搜索
 * dfs
 * 
 * @author vccyb
 *
 */
public class P002 {

	//重复
	//变化
	//边界
	
	static int dfs(int i, int j){
		if(i==3||j==4) return 1;
		return dfs(i+1,j) + dfs(i,j+1);
	}
	
	public static void main(String[] args) {
		int ans = dfs(0,0);
		System.out.println(ans);
	}
}

35

P03 梅森素数

package Code2013;

import java.math.BigInteger;

/**
 * 
 * 梅森素数
 * @author vccyb
 *
 */

public class P003 {
	
	
	
	public static void main(String[] args) {
		BigInteger x = BigInteger.valueOf(2).pow(11213).subtract(BigInteger.ONE);
		//2^11213 - 1
		String line = x.toString();
		String ans = line.substring(line.length()-100, line.length());
		System.out.println(line.length());
		System.out.println(ans.length());
		System.out.println(ans);
	}
}

大数类 BigInteger

最后一百位
a.length()-100, a.length()

ans:

3376
100
8586718527586602439602335283513944980064327030278104224144971883680541689784796267391476087696392191

P04 颠倒的价格

package Code2013;

import java.util.ArrayList;

/**
 * 
 * 
 * 颠倒
 * @author vccyb
 *
 */
public class P004 {

	/**
	 * 
	 * 枚举4位数，简单筛选
	 *颠倒做差，200多的放入一个集合，800多的放入一个集合
	 *遍历两个集合，检查是否相加为558
	 *输出结果
	 * @param args
	 */
	
	
	public static void main(String[] args) {
		
		ArrayList<Price> a1 = new ArrayList<Price>();
		ArrayList<Price> a2 = new ArrayList<Price>();
		
//		System.out.println(reverse("1958"));
//		System.out.println(reverse("5456"));
		
		
		for(int i=1000;i<10000;i++){
			//颠倒？
			String s = ""+i;
			if(s.contains("3")||s.contains("4")||s.contains("7"))continue;
			String re_s = reverse(s);

			int i1 = Integer.parseInt(re_s);
			int plus = i1 - i; //
//			System.out.println(s+" "+re_s);
//			System.out.println(i1+" "+plus);
			if(plus<-200&&plus>-300) a1.add(new Price(i, plus));
			if(plus<900&&plus>800) a2.add(new Price(i, plus));

		}
		
		for(Price p1:a1){
			for(Price p2:a2){
				if(p1.plus+p2.plus==558){
					System.out.println(p1.p+" "+p1.plus);
					System.out.println(p2.p+" "+p2.plus);
				}
			}
		}
		
		
	}
	
	private static String reverse(String s){
		// 
		char[] ans = new char[s.length()];
		for(int i=s.length()-1,j=0;i>=0;j++,i--){
			char c = s.charAt(j);
			if(c=='6')ans[i]='9';
			else if(c=='9')ans[i]='6';
			else ans[i]=c;
		}
		

		
		return new String(ans);
	}
	
	
	private static class Price{
		int p; //原价
		int plus;//颠倒价格-原价
		public Price(int p, int plus){
			this.p = p;
			this.plus = plus;
		}
	}
	
	
}

ans 9088

P07 错误票据

package Code2013;




import java.io.*;
import java.util.*;
public class P007 {
	
	
	/**
	 * 错误票据
	 * 
	 * @param args
	 */
	
	
	public static void main(String[] args) throws IOException {
		
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		ArrayList<Integer> list = new ArrayList<Integer>();
		int N = Integer.parseInt(br.readLine());
		for(int i=0;i<N;i++){
			String[] line = br.readLine().split(" ");
			for(int j=0;j<line.length;j++){
				list.add(Integer.parseInt(line[j]));
			}
		}
		
		//排序
		Collections.sort(list);  //注意：list的排序是用collections类
		
		
		int a=0,b=0; //a断号，b重号
		for(int i=1;i<list.size();i++){
			if(list.get(i)-list.get(i-1)==2){
				a = list.get(i)-1;
			}
			
			if(list.get(i).equals(list.get(i-1))){
				b = list.get(i);
			}
		}
		
		
		System.out.println(a+" "+b);
	}
}

P08 带分数

全排列是很重要的

    static int[] arr = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
    public static void qpl(int k) {
        if (k == arr.length) {
            check();
            return;
        }
        for (int i = k; i < arr.length; i++) {
            int temp = arr[i];
            arr[i] = arr[k];
            arr[k] = temp;
            qpl(k + 1);
            temp = arr[i];
            arr[i] = arr[k];
            arr[k] = temp;
        }
    }

package Code2013;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Scanner;

public class P008 {
	
	
	static int[] arr = {1,2,3,4,5,6,7,8,9};
	static int n;
	static int ans=0;
	public static void main(String[] args) throws IOException {
		Scanner sc = new Scanner(System.in);
		n = sc.nextInt();
		qpl(0);
		System.out.println(ans);
	}
	
	
	static void qpl(int x){
		if(x==arr.length){
//			System.out.println("全排列结果:");
//			for(int i=0;i<arr.length;i++){
//				System.out.print(arr[i]);
//			}
//			System.out.println();
			
			check();
			return;
		}
		
		for(int i=x;i<arr.length;i++){
			int t = arr[i];
			arr[i]=arr[x];
			arr[x] = t;
			
			qpl(x+1);
			//回溯
			t = arr[i];
			arr[i]=arr[x];
			arr[x] = t;
			
		}
	}
	
	
	static void check(){
		for(int i=0;i<arr.length-2;i++){
			int num1 = f(0,i);
			if(num1<n){
				for(int j=i+1;j<arr.length-1;j++){
					int num2 = f(i+1,j);
					int num3 = f(j+1,arr.length-1);
					if(num1+num2/num3==n&&num3%num2==0){
						ans++;
					}
				}
			}
		}
	}
	
	
	static int f(int left,int right){
		int sum = 0;
		for(int i=left;i<=right;i++){
			sum = sum*10 + arr[i];
		}
		return sum;
	}

}