蓝桥日记⑥2013第四届省赛（软件类）JavaA组@答案解析
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【蓝桥日记⑥】2013第四届省赛（软件类）JavaA组@答案解析
文章目录
1、世界末的星期
解法：日期函数Calendar
package fourSession;
import java.util.Calendar;
/*** 2013第四届省赛 1、世纪末的星期 ***/
public class test1
public static void main(String[] args)
Calendar calendar = Calendar.getInstance();
int year = 1999;
for (year = 1999; year < 1000000; year += 100)
calendar.set(year, 11, 31);
if (calendar.get(Calendar.DAY_OF_WEEK) == 1) break;
System.out.println(year);
答案：
2299
2、振兴中华
解法：dfs
package fourSession;
/*** 2013第四届省赛 2、振兴中华 ***/
public class test2
// 从 我 做 起 振 兴 中 华
// 1 2 3 4 5 6 7 8
static int[][] g = 1, 2, 3, 4, 5, 2, 3, 4, 5, 6, 3, 4, 5, 6, 7, 4, 5, 6, 7, 8;
static int ans = 0;
public static void main(String[] args)
dfs(0, 0, 1);
System.out.println(ans);
private static void dfs(int x, int y, int pre)
if (x == 3 && y == 4)
ans++;
return;
if (x + 1 < 4 && g[x + 1][y] == pre + 1) dfs(x + 1, y, pre + 1);
if (y + 1 < 5 && g[x][y + 1] == pre + 1) dfs(x, y + 1, pre + 1);
答案：
35
3、梅森素数
解法：BigInteger
package fourSession;
import java.math.BigInteger;
/*** 2013第四届省赛 3、梅森素数 ***/
public class test3
public static void main(String[] args)
BigInteger x = BigInteger.TWO;
x = x.pow(11213);
x = x.subtract(BigInteger.ONE);
String sx = x.toString();
String ans = sx.substring(sx.length() - 100, sx.length());
System.out.println(ans);
答案：
8586718527586602439602335283513944980064327030278104224144971883680541689784796267391476087696392191
4、颠倒的价牌
解法：暴力枚举
package fourSession;
import java.io.CharArrayReader;
import java.util.ArrayList;
/*** 2013第四届省赛 4、颠倒的价牌 ***/
public class test4
static class Price
int p; //原价
int rp; //颠倒价
Price(int p, int rp)
this.p = p;
this.rp = rp;
static ArrayList<Price> a1 = new ArrayList<>();
static ArrayList<Price> a2 = new ArrayList<>();
public static void main(String[] args)
// 枚举四位数，简单筛选，将赔200多的和赚800多的分别加入集合
// 遍历集合的两两组合，求差为558的组合
for (int i = 1000; i <= 9999; i++)
int ri = reverseI(i);
if (i - ri > -300 && i - ri < -200) a1.add(new Price(i, ri));
if (i - ri > 800 && i - ri < 900) a2.add(new Price(i, ri));
boolean find = false;
for (Price a : a1)
for (Price b : a2)
if (a.p - a.rp + b.p - b.rp ==558)
System.out.println(a.rp);
find = true;
break;
if (find) break;
private static int reverseI(int x)
char[] cs = (x + "").toCharArray();
if (cs[0] == '0' || cs[3] == '0') return 1;
int ans = 0, t = 1;
for (int i = 0; i < 4; i++)
if (cs[i] == '3' || cs[i] == '4' || cs[i] == '7') return 1;
if (cs[i] == '2')
cs[i] = '5';
else if (cs[i] == '5')
cs[i] = '2';
else if (cs[i] == '6')
cs[i] = '9';
else if (cs[i] == '9')
cs[i] = '6';
ans += t * (cs[i] - '0');
t *= 10;
return ans;
答案：
9088
5、三部排序
解法：三向切分排序
有兴趣的可以看看我之前的总结：排序算法总结☑▁▂▃▅▂▃▁▂▃▇▆▃▂▁
package fourSession;
/*** 2013第四届省赛 5、三部排序 ***/
public class test5
static void sort(int[] x)
int p = 0;
int left = 0;
int right = x.length - 1;
while (p <= right)
if (x[p] < 0)
int t = x[left];
x[left] = x[p];
x[p] = t;
left++;
p++;
else if (x[p] > 0)
int t = x[right];
x[right] = x[p];
x[p] = t;
right--;
//p++;
else
p++;
show(x);
static void show(int[] x)
for (int i = 0; i < x.length; i++)
System.out.print(x[i] + ",");
System.out.println();
public static void main(String[] args)
//int[] x = 25,18,-2,0,16,-5,33,21,0,19,-16,25,-3,0;
sort(new int[]-1, 0, 1, -2, 0, 2, -3, 0, 0, 3, -4, -5, 4, -6, 0, 5, 6);
sort(new int[]-1, 0, -1, -2, 0, -2, -3, 0, 0, -3, -4, -5, -4, -6, 0, -5, -6);
sort(new int[]1, 0, 1, 2, 0, 2, 3, 0, 0, 3, 4, 5, 4, 6, 0, 5, 6);
答案：
p++
6、逆波兰表达式
package fourSession;
/*** 2013第四届省赛 6、逆波兰表达式 ***/
public class test6
static int[] evaluate(String x)
if (x.length() == 0) return new int[]0, 0;
char c = x.charAt(0);
if (c >= '0' && c <= '9') return new int[]c - '0', 1;
int[] v1 = evaluate(x.substring(1));
int[] v2 = evaluate(x.substring(1 + v1[1]));
int v = Integer.MAX_VALUE;
if (c == '+') v = v1[0] + v2[0];
if (c == '*') v = v1[0] * v2[0];
if (c == '-') v = v1[0] - v2[0];
return new int[]v, 1 + v1[1] + v2[1];
public static void main(String[] args)
System.out.println(evaluate("-+3*5+261")[0]);
System.out.println(evaluate("+*35*42")[0]);
答案：
evaluate(x.substring(1 + v1[1]))
7、错误票据
解法一：List排序
package fourSession;
import java.util.*;
/*** 2013第四届省赛 7、错误票据 ***/
public class test7
public static void main(String[] args)
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
ArrayList<Integer> list = new ArrayList();
sc.nextLine();
for (int i = 0; i < n; i++)
String s = sc.nextLine();
String[] ss = s.split(" ");
for (int j = 0; j < ss.length; j++)
list.add(Integer.parseInt(ss[j]));
sc.close();
int less = 0, same = 0;
Collections.sort(list);
for (int i = 1; i < list.size(); i++)
if (list.get(i).equals(list.get(i - 1))) same = list.get(i);
if (list.get(i - 1) + 2 == list.get(i)) less = list.get(i) - 1;
System.out.println(less + " " + same);
解法二：Set集合去重
package fourSession;
import java.util.ArrayList;
import java.util.Scanner;
import java.util.TreeSet;
/*** 2013第四届省赛 7、错误票据 ***/
public class test7
public static void main(String[] args)
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
ArrayList<Integer> list = new ArrayList();
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