1
import java.util.Scanner;
public class Main{
public static void main(String[] args){
final int NUMBER = 100;
int count = 0;
Scanner input = new Scanner(System.in);
while(count < NUMBER){
System.out.print(getPentagonalNumber(count+1) + " ");
if((count+1) % 10 == 0)
System.out.println();
++count;
}
}
public static int getPentagonalNumber(int n){
return n*(3*n-1)/2;
}
}
2
import java.util.Scanner;
public class Main{
public static void main(String[] args){
Scanner input = new Scanner(System.in);
int n = input.nextInt();
System.out.println(sumDigits(n));
}
public static int sumDigits(int n){
int sum = 0;
while(n != 0){
sum += n % 10;
n = n / 10;
}
return sum;
}
}
3import java.util.Scanner; public class Main{ public static void main(String[] args){ Scanner input = new Scanner(System.in); int num = input.nextInt(); if(isPalindrome(num)) System.out.println(num + " is palindrome."); else System.out.println(num + " is not palindrome."); } public static int reverse(int number){ int num = 0; while(number != 0){ num = num*10 + number%10; number /= 10; } return num; } public static boolean isPalindrome(int number){ if(number == reverse(number)) return true; return false; } }4import java.util.Scanner; public class Main{ public static void main(String[] args){ Scanner input = new Scanner(System.in); int num = input.nextInt(); System.out.println(reverse(num)); } public static int reverse(int number){ int num = 0; while(number != 0){ num = num*10 + number%10; number /= 10; } return num; }}5import java.util.Scanner; public class Main{ public static void main(String[] args){ Scanner input = new Scanner(System.in); double num1 = input.nextDouble(); double num2 = input.nextDouble(); double num3 = input.nextDouble(); displaySortedNumber(num1,num2,num3); } public static void displaySortedNumber(double num1, double num2, double num3){ double temp = 0; if(num1 > num2){ temp = num1; num1 = num2; num2 = temp; } if(num1 > num3){ temp = num1; num1 = num3; num3 = temp; } if(num2 > num3){ temp = num2; num2 = num3; num3 = temp; } System.out.println(num1 + " " + num2 + " " + num3); }}6import java.util.Scanner; public class Main{ public static void main(String[] args){ Scanner input = new Scanner(System.in); int num = input.nextInt(); displayPattern(num); } public static void displayPattern(int n){ for(int i = 1; i <= n; ++i){ for(int j = 1; j <= n-i; ++j) System.out.print(" "); for(int j = i; j > 0; --j) System.out.print(j); System.out.println(); } }}7，8，9套公式10import java.util.Scanner; public class Main{ public static void main(String[] args){ int count = 0; for(int i = 1; i <= 10000; ++i){ if(isPrime(i)) ++count; } System.out.println(count); } public static boolean isPrime(int n){ if(n == 1) return false; for(int i = 2; i*i <= n; ++i){ if(n%i == 0) return false; } return true; }}11。。。。12import java.util.Scanner; public class Main{ public static void main(String[] args){ printChars('1','Z',10); } public static void printChars(char ch1, char ch2, int numberPerLine){ int count = 0; for(int i = ch1; i <= ch2; ++i){ System.out.print((char)i); ++count; if(count%10 == 0) System.out.println(); } }}13import java.util.Scanner; public class Main{ public static void main(String[] args){ for(int i = 1; i <= 20; ++i){ System.out.println(i + " " + m(i)); } } public static double m(int n){ double sum = 0.0; for(int i = 1; i <= n; ++i) sum += (double)i/(double)(i+1); return sum; }}14import java.util.Scanner; public class Main{ public static void main(String[] args){ for(int i = 1; i <= 901; i += 100){ System.out.println(i + " " + m(i)); } } public static double m(int n){ double sum = 0.0; int one = 1; for(int i = 1; i <= n; ++i){ sum += one/(double)(2*i-1); one = -one; } return 4*sum; }}15，16。。。。。。。17import java.util.Scanner; public class Main{ public static void main(String[] args){ Scanner input = new Scanner(System.in); int n = input.nextInt(); printMatrix(n); } public static void printMatrix(int n){ for(int i = 0; i < n; ++i){ for(int j = 0; j < n; ++j){ System.out.print((System.currentTimeMillis()/(j+i+1))%2 + " "); } System.out.println(); } }}18import java.util.Scanner; public class Main{ public static void main(String[] args){ Scanner input = new Scanner(System.in); System.out.print("Enter password:"); String password = input.next(); if(isValidPassWord(password)){ System.out.println("Valid Password"); } else System.out.println("Invalid Password"); } public static boolean isValidPassWord(String str){ if(str.length() < 8) return false; int count = 0; for(int i = 0; i < str.length(); ++i){ if(!Character.isDigit(str.charAt(i)) && !Character.isLetter(str.charAt(i))) return false; if(Character.isDigit(str.charAt(i))) ++count; } if(count < 2) return false; return true; }}19，20，21。。。。。。22import java.util.Scanner; public class Main{ public static void main(String[] args){ Scanner input = new Scanner(System.in); double n = input.nextDouble(); System.out.println(sqrt(n)); } public static double sqrt(double n){ double nextGuess = 0; double lastGuess = 1.0; while(true){ nextGuess = (lastGuess + n/lastGuess) / 2; if(Math.abs(nextGuess - lastGuess) < 0.0001) return nextGuess; lastGuess = nextGuess; } }}23。。。。。24参考第五章29题25貌似和程序清单2-7差不多26import java.util.Scanner; public class Main{ public static void main(String[] args){ int count = 0; int i = 1; while(count < 100){ if(isPrime(i) && isPalindrome(i)){ System.out.print(i + " "); ++count; if(count % 10 == 0) System.out.println(); } ++i; } } public static boolean isPalindrome(int number){ if(number == reverse(number)) return true; return false; } public static int reverse(int number){ int num = 0; while(number != 0){ num = num*10 + number%10; number /= 10; } return num; } public static boolean isPrime(int n){ if(n == 1) return false; for(int i = 2; i*i <= n; ++i){ if(n%i == 0) return false; } return true; }}27import java.util.Scanner; public class Main{ public static void main(String[] args){ int count = 0; int i = 1; while(count < 100){ if(isPrime(i) && isPrime(reverse(i))){ System.out.print(i + " "); ++count; if(count % 10 == 0) System.out.println(); } ++i; } } public static int reverse(int number){ int num = 0; while(number != 0){ num = num*10 + number%10; number /= 10; } return num; } public static boolean isPrime(int n){ if(n == 1) return false; for(int i = 2; i*i <= n; ++i){ if(n%i == 0) return false; } return true; }}28import java.util.Scanner; public class Main{ public static void main(String[] args){ for(int p = 1; p <= 31; ++p){ int n = (int)Math.pow(2, p)-1; if(isPrime(n)) System.out.println(p + " " + n); } } public static boolean isPrime(int n){ if(n == 1) return false; for(int i = 2; i*i <= n; ++i){ if(n%i == 0) return false; } return true; }}29import java.util.Scanner; public class Main{ public static void main(String[] args){ int record = 2; for(int i = 3; i <= 1000; ++i){ if(isPrime(i)){ if(i - record == 2){ System.out.println("(" + record + ", " + i + ")"); record = i; } else if(i - record < 2 && !isPrime(i+1)) record = i; else if(i - record > 2) record = i; } } } public static boolean isPrime(int n){ if(n == 1) return false; for(int i = 2; i*i <= n; ++i){ if(n%i == 0) return false; } return true; }}30。。。。。。31import java.util.Scanner;public class Main {public static void main(String[] args){Scanner cin = new Scanner(System.in);long num = cin.nextLong();int size = getSize(num);boolean flag = false;if(prefixMatched(num,4) || prefixMatched(num,5) || prefixMatched(num,37) || prefixMatched(num,6))flag = true;if(size >= 13 && size <= 16 && flag && isValid(num)){System.out.println(num + " is valid");}else{System.out.println(num + " is invalid");}}public static boolean isValid(long number){int sum1 = sumOfDoubleEvenPlace(number);int sum2 = sumOfOddPlace(number);int sum = sum1+sum2;if(sum%10 == 0) return true;else return false;}public static int sumOfDoubleEvenPlace(long number){int len = 0;int sum = 0;int[] numarr = new int[20];int index = 0;while(number != 0){numarr[index++] = (int)(number%10);number /= 10;}for(int i = index-1; i >= 0; --i){++len;if(len%2 == 1){sum += getDigit(numarr[i]*2);}}return sum;}public static int getDigit(int number){if(number < 10)return number;return (number%10 + number/10);}public static int sumOfOddPlace(long number){int len = 0;int sum = 0;int[] numarr = new int[20];int index = 0;while(number != 0){numarr[index++] = (int)(number%10);number /= 10;}for(int i = index-1; i >= 0; --i){++len;if(len%2 == 0){sum += numarr[i];}}return sum;}public static boolean prefixMatched(long number, int d){String str = String.valueOf(number);String substr = String.valueOf(d);if(str.startsWith(substr))return true;return false;}public static int getSize(long d){int len = 0;while(d != 0){d /= 10;++len;}return len;}//感觉题目用不到这个方法啊public static long getPrefix(long number, int k){return 0;}}
待续。。。。。