「藍橋杯」練習系統練習題答案（本身作的）

題目來源：

藍橋杯練習系統（寫博客日期爲2019.3.23，因此可能讀者看到的時候，更新了新的題）

這裏只提供每道題的個人解題代碼，僅供參考。這裏不會寫解題思路和詳解，若是有須要的話，請留言給我，我會在留言區回覆。vip題目來源dotcpp（順序跟練習系統同樣，只不過我沒有vip，因此在dotcpp網站中看題並解題）。

試題集截圖： 

 

入門訓練：

1-1  BEGIN-1  A+B問題

import java.util.*; public class Main { public static void main(String[] args){ Scanner in = new Scanner(System.in); int a = in.nextInt(); int b = in.nextInt(); System.out.println(a+b); } }

1-2  BEGIN-2  序列求和

import java.util.*; public class Main { public static void main(String[] args){ Scanner in = new Scanner(System.in); double n = in.nextInt(); double s = (1 + n) / 2; double t = s * n; System.out.println((long)t); } }

1-3  BEGIN-3  圓的面積

import java.util.*; public class Main { public static void main(String[] args){ Scanner in = new Scanner(System.in); final double PI = 3.14159265358979323; double a = in.nextInt(); double c = a*a*PI; System.out.printf("%.7f", c); } }

1-4  BEGIN-4  Fibonacci數列

public class Main { public static void main(String[] ars){ Scanner in = new Scanner(System.in); int n = in.nextInt(); if(n < 3){ System.out.println(1); }else { int[] a = new int[n + 1]; a[1] = 1 % 10007; a[2] = 1 % 10007; for (int i = 3; i <= n; i++) { a[i] = (a[i - 1] + a[i - 2]) % 10007; } System.out.println(a[n]); } } }

基礎練習：

2-1  BASIC-1  閏年判斷

import java.util.Scanner; public class Main { public static void main(String[] args){ Scanner in = new Scanner(System.in); int y = in.nextInt(); if((y%4 == 0 && y%100 != 0) || (y%400 == 0)){ System.out.println("yes"); }else { System.out.println("no"); } } } 

2-2  BASIC-2  01字串

public class Main { public static void main(String[] args){ for(int i=0; i<32; i++) { String str = Integer.toBinaryString(i); System.out.printf("%05d", Integer.valueOf(str)); System.out.println(); } } } 

2-3  BASIC-3  字母圖形

import java.util.Scanner; public class Main { public static void main(String[] args){ Scanner in = new Scanner(System.in); int n = in.nextInt(); int m = in.nextInt(); String s = "BCDEFGHIJKLMNOPQRSTUVWXYZ"; StringBuilder str = new StringBuilder(s); str = str.reverse(); str.append("A"); str.append(s); int a = str.indexOf("A"); int b = a+m; for(int i=0; i<n; i++){ System.out.println(str.substring(a, b)); a--; b--; } } } 

2-4  BASIC-4  數列特徵

import java.util.Scanner; public class Main { public static void main(String[] args){ Scanner in = new Scanner(System.in); int n = in.nextInt(); int[] s = new int[n]; for(int i=0; i<n; i++){ s[i] = in.nextInt(); } int max = s[0]; int min = s[0]; int sum = 0; for(int j=0; j<s.length; j++){ if(s[j] > max){ max = s[j]; } if(s[j] < min){ min = s[j]; } sum = sum + s[j]; } System.out.println(max); System.out.println(min); System.out.println(sum); } } 

2-5  BASIC-5  查找整數

import java.util.Scanner; public class Main { public static void main(String[] args){ Scanner in = new Scanner(System.in); int n = in.nextInt(); int[] s = new int[n]; for(int i=0; i<n; i++){ s[i] = in.nextInt(); } int a = in.nextInt(); in.close(); int count = 0; for(int j=0; j<s.length; j++){ if(s[j] == a){ count = j+1; break; } } if(count == 0){ System.out.println(-1); }else { System.out.println(count); } } } 

2-6  BASIC-6  楊輝三角形

import java.util.Scanner; public class Main { public static void main(String[] args){ Scanner in = new Scanner(System.in); int n = in.nextInt(); int[][] a = new int[n][n]; if(n == 1){ System.out.println(1); }else{ a[0][0] = 1; for(int i=1; i<n; i++){ a[i][0] = 1; a[i][i] = 1; if(n != 2){ for(int j=1; j<=i-1; j++){ a[i][j] = a[i-1][j-1] + a[i-1][j]; } } } } // 顯示 for(int i=0; i<n; i++){ for(int j=0; j<=i; j++){ System.out.print(a[i][j]); if(i!=j){ System.out.print(' '); } } System.out.println(); } } } 

2-7  BASIC-7  特殊的數字

public class Main { public static void main(String[] args){ for(int dd=100; dd<=999; dd++){ String data = dd + ""; char d0 = data.charAt(0); char d1 = data.charAt(1); char d2 = data.charAt(2); double sum1 = Math.pow((d0-'0'), 3) + Math.pow((d1-'0'), 3) + Math.pow((d2-'0'), 3); if((int)sum1 == dd){ System.out.println(dd); } } } } 

2-8  BASIC-8  迴文數

public class Main {
    public static void main(String[] args){
        StringBuilder a = new StringBuilder();
        for(int i=1; i<=9; i++){
            for(int j=0; j<=9; j++){
                a.append(i);
                a.append(j);
                a.append(j);
                a.append(i);
                System.out.println(a.toString());
                a.delete(0, a.length());
            }
        }
    }
}

2-9  BASIC-9  特殊迴文數 

2-9-1  解法一

import java.util.Scanner; public class Main { public static void main(String[] args){ Scanner in = new Scanner(System.in); int n = in.nextInt(); for(int i=10000; i<=999999; i++){ String data = "" + i; int sum = 0; for(int k=0; k<data.length(); k++){ sum = sum + (data.charAt(k)-'0'); } int len = data.length(); int count = len/2; // 計算相等的個數，若是是2，3則知足 StringBuilder flag = new StringBuilder(); for(int j=0; j<count; j++){ if(data.charAt(j) == data.charAt(len-j-1)){ flag.append(1); }else{ flag.append(0); } } if((flag.toString().equals("111") || flag.toString().equals("11")) && (n == sum)){ System.out.println(i); } else{ continue; } } } } 

2-9-2  解法二

import java.util.Scanner; public class Main { public static void f5(int n){ /* 五位數處理代碼 */ StringBuilder anser1 = new StringBuilder(); // 測試第1位的值 for(int i=1; i<=9; i++){ // 測試第2位的值 for(int j=0; j<=9; j++){ // 計算第3位的值 int third_number = n - 2*i - 2*j; if(third_number>=0 && third_number<=9){ anser1.append(i); anser1.append(j); anser1.append(third_number); anser1.append(j); anser1.append(i); System.out.println(anser1); anser1.delete(0, anser1.length()); }else{ continue; } } } } public static void f6(int n){ /* 六位數處理代碼 */ StringBuilder anser2 = new StringBuilder(); // temp: 前三位相加的值 int temp = n/2; // 測試第1位的值 for(int i=1; i<=9; i++){ // 測試第2位的值 for(int j=0; j<=9; j++){ // 計算第3位的值 int third_number2 = temp-i-j; if(third_number2>=0 && third_number2<=9){ anser2.append(i); anser2.append(j); anser2.append(third_number2); anser2.append(third_number2); anser2.append(j); anser2.append(i); System.out.println(anser2); anser2.delete(0, anser2.length()); }else{ continue; } } } } public static void main(String[] args){ Scanner in = new Scanner(System.in); int n = in.nextInt(); f5(n); // 偶數纔多是6位 if(n%2==0){ f6(n); } } } 

2-10  BASIC-10  十進制轉十六進制

import java.util.Scanner; public class Main { public static char f(long a){ char temp = ' '; if(a<=9){ temp = (char)(a+48); }else { switch ((int) a) { case 10: temp = 'A'; break; case 11: temp = 'B'; break; case 12: temp = 'C'; break; case 13: temp = 'D'; break; case 14: temp = 'E'; break; case 15: temp = 'F'; break; } } // System.out.println(temp); return temp; } public static void main(String[] args){ Scanner in = new Scanner(System.in); long a = in.nextLong(); StringBuilder ss = new StringBuilder(); if(a == 0){ ss.append(0); }else { while (a != 0) { long number = a % 16; char s = f(number); ss.append(s); a = a / 16; } } System.out.println(ss.reverse().toString()); } } 

2-11  BASIC-11  十六進制轉十進制

import java.util.*; public class Main { public static int f(char a){ int x=0; if(a>='0' && a<='9'){ x = a-'0'; }else{ switch (a){ case 'A': x = 10;break; case 'B': x = 11;break; case 'C': x = 12;break; case 'D': x = 13;break; case 'E': x = 14;break; case 'F': x = 15;break; default:break; } } return x; } public static void h(String str){ int len = str.length(); double x = 0; for(int i=0; i<len; i++){ int value = f(str.charAt(i)); x = value*Math.pow(16, len-1-i) + x; } System.out.println((long)x); } public static void main(String[] args){ Scanner in = new Scanner(System.in); String a = in.next(); in.close(); h(a); } } 

2-12  BASIC-12  十六進制轉八進制

import java.util.Scanner; public class Main { public static String f(String s){ int len = s.length(); StringBuilder str = new StringBuilder(); for(int i=0; i<len; i++){ switch (s.charAt(i)){ case '0': str.append("0000");break; case '1': str.append("0001");break; case '2': str.append("0010");break; case '3': str.append("0011");break; case '4': str.append("0100");break; case '5': str.append("0101");break; case '6': str.append("0110");break; case '7': str.append("0111");break; case '8': str.append("1000");break; case '9': str.append("1001");break; case 'A': str.append("1010");break; case 'B': str.append("1011");break; case 'C': str.append("1100");break; case 'D': str.append("1101");break; case 'E': str.append("1110");break; case 'F': str.append("1111");break; default: break; } } return str.toString(); } public static void g(String str){ int len = str.length(); StringBuilder a = new StringBuilder(); for(int i=0; i<len; i+=3){ int temp = (str.charAt(i)-'0')*4+(str.charAt(i+1)-'0')*2+(str.charAt(i+2)-'0'); a.append(temp); } System.out.println(a.toString().replaceFirst("^0*", "")); } public static void main(String[] args){ Scanner in = new Scanner(System.in); int n = in.nextInt(); String[] a = new String[n]; for(int i=0; i<n; i++){ a[i] = in.next(); } in.close(); for(int j=0; j<n; j++){ String str2 = f(a[j]); int len2 = str2.length(); if(len2 % 3 == 1){str2 = "00" + str2;} else if(len2 % 3 == 2){str2 = "0" + str2;} g(str2); } } } 

2-13  BASIC-13  數列排序

import java.util.*; public class Main { public static void main(String[] args){ Scanner in = new Scanner(System.in); int n = in.nextInt(); int[] a = new int[n]; for(int i=0; i<n; i++){ a[i] = in.nextInt(); } for(int j=0; j<n-1; j++){ for(int k=j+1; k<n; k++){ if(a[j]>a[k]){ int tt = a[k]; a[k] = a[j]; a[j] = tt; } } } for(int j=0; j<n; j++){ System.out.print(a[j]); if(j != n-1){ System.out.print(" "); } } } } 

未完待續。。。（更新於2019.3.23）