2017年第八届蓝桥杯参赛 Java B 组真题

2017年第八届蓝桥杯参赛 Java B 组真题

第一题

import java.util.Scanner;

public class Q1 {

	static double price, discount, sum = 0;
	
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		while (sc.hasNext()) {
			sc.next();
			price = Double.parseDouble(sc.next());
			String str = sc.next();
			if ("半价".equals(str))
				discount = 0.5;
			else if (str.length() == 2)
				discount = 0.1 * (str.charAt(0) - '0');
			else 
				discount = 0.01 * Integer.parseInt(str.substring(0, 2));
			sum += price * discount;
		}
		System.out.println(sum);
	}
}

答案：5200

第二题

public class Q2 {

	static int[] a = new int[15];
	static boolean[] book = new boolean[15];
	static int ans = 0;
	
	static void dfs(int step) {
		if (step == 10) {
			judge();
			return;
		}
		for (int i = 1; i < 10; i++) {
			if (!book[i]) {
				book[i] = true;
				a[step] = i;
				dfs(step + 1);
				book[i] = false;
			}
		}
	}

	static void judge() {
		int sum = sum(1, 4);
		if (sum != sum(4, 7)) return;
		if (sum != sum(7, 9) + a[1]) return;
		ans++;
	}
	
	static int sum(int s, int e) {
		int res = 0;
		for (int i = s; i <= e; i++)
			res += a[i];
		return res;
	}
	
	public static void main(String[] args) {
		dfs(1);
		System.out.println(ans / 3 / 2);
	}
}

答案：144

第三题

import java.util.Scanner;

public class Q3 {
	
	static double[][] a = new double[40][40];

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		for (int i = 1; i < 30; i++) {
			for (int j = 1; j <= i; j++) {
				a[i][j] = sc.nextDouble();
			}
		}
		
		for (int i = 1; i < 30; i++) {
			for (int j = 1; j <= i; j++) {
				a[i + 1][j] += a[i][j] / 2;
				a[i + 1][j + 1] += a[i][j] / 2;
			}
		}
		
		double min = Double.MAX_VALUE, max = 0;
		for (int i = 1; i <= 30; i++) {
			min = Math.min(min, a[30][i]);
			max = Math.max(max, a[30][i]);
		}
		
		// 2086458231 / min = x / max
		System.out.println((long)(2086458231 * max / min));
	}
}

答案：72665192664

第五题

public class Q5
{
	static int len(int x){
		if(x<10) return 1;
		return len(x/10)+1;
	}
	
	// 取x的第k位数字
	static int f(int x, int k){
		if(len(x)-k==0) return x%10;
		return f(x / 10, k);  //填空
	}
	
	public static void main(String[] args)
	{
		int x = 23513;
		//System.out.println(len(x));
		System.out.println(f(x,3));
	}
}

第六题

public class Q6
{
	static int f(String s1, String s2)
	{
		char[] c1 = s1.toCharArray();
		char[] c2 = s2.toCharArray();
		
		int[][] a = new int[c1.length+1][c2.length+1];
		
		int max = 0;
		for(int i=1; i<a.length; i++){
			for(int j=1; j<a[i].length; j++){
				if(c1[i-1]==c2[j-1]) {
					a[i][j] = a[i - 1][j - 1] + 1;  //填空 
					if(a[i][j] > max) max = a[i][j];
				}
			}
		}
		
		return max;
	}
	
	public static void main(String[] args){
		int n = f("abcdkkk", "baabcdadabc");
		System.out.println(n);
	}
}

第七题

import java.util.ArrayList;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Scanner;
import java.util.Set;

public class Q7 {
	
	static int[] days = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
	// a[0] -> 年, a[1] -> 月, a[2] -> 日 
	static int[] a = new int[3];
	static List<String> list = new ArrayList<>();
	static Set<String> set = new HashSet<>();

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String str = sc.next();
		String[] strs = str.split("\\/");
			
		set_y_m_d(strs);
		judge();
		set_m_d_y(strs);
		judge();
		set_d_m_y(strs);
		judge();
		
		Collections.sort(list);
		for (String t : list)
			System.out.println(t);
	}
	
	static void judge() {
		a[0] += 1900; 
		if (check() && !set.contains(_2time())) {
			list.add(_2time());
			set.add(_2time());
		}
		a[0] += 100;
		if (check() && !set.contains(_2time())) {
			list.add(_2time());
			set.add(_2time());
		}
	}
	
	static boolean check() {
		if (a[0] < 1960 || a[0] > 2059) return false;
		if (a[1] < 1 || a[1] > 12) return false;
		if (a[1] == 2 && a[2] == 29 && isRun(a[0])) return true;
		return a[2] <= days[a[1]] && a[2] > 0; 
	}
	
	static boolean isRun(int y) {
		return (y % 4 == 0 && y % 100 != 0) || (y % 400 == 0);
	}
	
	static int str2int(String str) {
		return (str.charAt(0) - '0') * 10 + (str.charAt(1) - '0');
	}
	
	static void set_y_m_d(String[] strs) {
		a[0] = str2int(strs[0]);
		a[1] = str2int(strs[1]);
		a[2] = str2int(strs[2]);
	}
	
	static void set_m_d_y(String[] strs) {
		a[1] = str2int(strs[0]);
		a[2] = str2int(strs[1]);
		a[0] = str2int(strs[2]);
	}
	
	static void set_d_m_y(String[] strs) {
		a[2] = str2int(strs[0]);
		a[1] = str2int(strs[1]);
		a[0] = str2int(strs[2]);
	}
	
	static String _2time() {
		String res = "";
		res += a[0] + "-";
		res += (a[1] >= 10 ? a[1] : "0" + a[1]) + "-";
		res += a[2] >= 10 ? a[2] : "0" + a[2];
		return res;
	}
}

第八题

import java.util.Scanner;

public class Q8 {
    
	static int MAX = 10000;
	static int n; 
	static int[] a = new int[100];
	static boolean[] dp = new boolean[MAX];
	static int min = 105, pre = 0, ans = 0;
	
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		n = sc.nextInt();
		for (int i = 0; i < n; i++) {
			a[i] = sc.nextInt();
			min = Math.min(min, a[i]);
		}
		
		dp[0] = true;
		for (int i = 1; i < MAX; i++) {
			if (i == MAX - 1) {
				System.out.println("INF");
				return;
			}
			
			for (int j = 0; j < n; j++) {
				if (i - a[j] >= 0) {
					dp[i] |= dp[i - a[j]];
				}
			}
			if (!dp[i]) pre = i;
			if (i - pre >= min) break;
		}
		
		for (int i = 1; i <= pre; i++) {
			if (!dp[i]) ans++;
		}
		
		System.out.println(ans);
	}
}

第九题

public class Q9 {

	static int MAX_N = 100005;
	static int n, k;
	static int[][] a = new int[MAX_N][2];
	
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		n = sc.nextInt();
		k = sc.nextInt();
		
		for (int i = 0; i < n; i++) {
			a[i][0] = sc.nextInt();
			a[i][1] = sc.nextInt();
		}
		
		int lo = 1, hi = 100000;
		while (lo <= hi) {
			int mid = (lo + hi) >>> 1;
			int cnt = 0;
			for (int i = 0; i < n; i++) {
				cnt += (a[i][0] / mid) * (a[i][1] / mid);
			}
			if (cnt >= k)
				lo = mid + 1;
			else 
				hi = mid - 1;
		}
		
		System.out.println(lo - 1);
	}
}