java经典算法50题答案

1package work;public class Fib {public static void main(String[] args){int[] fib = new int[23];fib[0] = 1;fib[1] = 1;for(int i = 2; i < fib.length; i++){fib[i] = fib[i - 1] + fib[i - 2];}for(int i = 0; i < fib.length; i++){System.out.print(fib[i]+" ");}}}2package work;import java.math.*;import java.util.ArrayList;public class Sushu {public static void main(String[] args){ArrayList list = new ArrayList();for(int i = 101; i < 200; i++){if(isPrime(i)){list.add(i);}}System.out.println(list + "共有" +list.size());}public static boolean isPrime(int i){boolean flag = true;for(int j = 2; j < Math.sqrt(i); j++){if(i % j == 0){flag = false;}}return flag;}}3package work;public class Flower {public static void main(String[] args){for(int i = 100; i <999; i++){if(flower(i)){System.out.print(i +" ");}}}public static boolean flower(int number){boolean flag = false;int i = number / 100; //int j = (number - i*100) / 10;int k = number % 10;if((i*i*i + j*j*j + k*k*k) == number){flag = true;}return flag;}}4package work;import java.util.Scanner;import java.io.*;public class Decomposition {private static int k = 2;public static void main(String[] args)throws IOException{ Scanner scanner = new Scanner(System.in);System.out.println("请输入一个整数");int number = scanner.nextInt();System.out.print(number + "=");fenJie(number);}public static void fenJie(int number){if(k == number){System.out.print(k);return;}else if(number % k == 0){System.out.print(k + "*");fenJie(number / k);}else{k++;fenJie(number);}}}5package work;import java.util.Scanner;import java.io.*;public class TiaoJian{public static void main(String[] args) throws IOException{ Scanner scanner = new Scanner(System.in);System.out.println("请输入成绩");int score = scanner.nextInt();char s = ((score >= 90) ? 'A' : ((score < 60) ? 'C' : 'B'));System.out.println(s);}}6package work;import java.util.Scanner;public class Beiyue{public static void main(String[] args){Scanner scanner = new Scanner(System.in);System.out.println("请输入m n");int m = scanner.nextInt();int n = scanner.nextInt();int a = yueshu(m,n);System.out.println("最大公约数为；" + a);System.out.println("最小公倍数为：" +m * n / a);}public static int yueshu(int m, int n){if(n == 0){return m;}else if(n != 0){return yueshu(n,m%n);}return 0;}}7package work;import java.util.Scanner;public class Fenlei{public static void main(String[] args){Scanner scanner = new Scanner(System.in);System.out.println("请输入一串字符：");String s = scanner.nextLine();char[] ch = s.toCharArray();int number = 0;int space = 0;int letter = 0;int other = 0;for(int i = 0; i < ch.length; i++){if(((ch[i] > 'a') && (ch[i] < 'z')) || ((ch[i] > 'A') && (ch[i] < 'Z'))){ //Character.isLetter(ch[i])letter++;}else if((ch[i] > '0') &&(ch[i] < '9')){ //Character.isDigit(ch[i])number++;}else if(ch[i] == ' '){ //Character.isSpaceChar(ch[i]) space++;}else{other++;}}System.out.println("letter = " + letter);System.out.println("number = " + number);System.out.println("space = " + space);System.out.println("other = " + other);}}8package work;import java.util.Scanner;public class Sum{public static void main(String[] args){Scanner scanner = new Scanner(System.in);System.out.println("请输入数字a");int a = scanner.nextInt();System.out.println("请输入加数个数");int n = scanner.nextInt();sum(a, n);}public static void sum(int a, int n){int sum = 0;int t = 0; //每一项的值System.out.println("sum = ");for(int i = 0; i < n; i++){t = 0; //初始化为0for(int j = 0; j <= i; j++){ //计算每一项的值t = t + (int)(Math.pow(10, j)) * a;}if(i < n - 1){System.out.print(t + "+");}sum = sum + t;}System.out.print(t);System.out.print("=" + sum);}}9package work;import java.io.*;public class Wanshu{private static int k = 2;private static int sum = 1;public static void main(String[] args){for(int number = 4; number < 1000; number++){ k = 2;sum =1;wanshu(number);}}public static int fenJie(int number){if(k == number){//System.out.print(k);sum = sum + k;}else if(number % k == 0){//System.out.print(k + " * ");sum = sum + k;fenJie(number / k);}else if(number % k != 0){k++;fenJie(number);}return sum;}public static void wanshu(int number){//System.out.print(number + "= 1 * ");int s = fenJie(number);//System.out.println();//System.out.println("因子之和为：" + s);if(s == number){System.out.print(number + " ");}}}10package work;public class Fantan{public static void main(String[] args){double length = 100;double height = 100;for(int i = 0; i < 10; i++){length = length + height;height = height / 2.0;}System.out.println(length);System.out.println(height);}}11package work;public class Pailie{public static void main(String[] args){int sum = 0;int num = 0;for(int i = 1; i <= 4; i++){for(int j = 1; j <= 4; j++){for(int k = 1; k <= 4; k++){if((k != j) && (k !=i) && (i != j)){num = 100 * i + 10 * j + k;System.out.print(num + " ");sum++;}}}}System.out.println("sum = " + sum);}}12package work;import java.util.Scanner;public class Pay{public static void main(String[] args){Scanner scanner = new Scanner(System.in);System.out.println("请输入工资：");int salary = scanner.nextInt();int n = salary / 10;double sum;switch(n){case 0 :sum = salary * 0.1; break;case 1 :sum = 1 + (salary - 10) * 0.075; break;case 2 :case 3 :sum = 1.75 + (salary - 20) * 0.05; break;case 4 :case 5 :sum = 2.75 + (salary - 40) * 0.03; break;case 6 :case 7 :case 8 :case 9 :sum = 3.35 + (salary - 60) * 0.015; break;default :sum = 3.95 + (salary - 100) * 0.1; break;}System.out.println("奖金为：" + sum);}}13package work;public class Pow{public static void main(String[] args){int number = 0;for(int i = 0; i < 320; i++){for(int j = 0; j < 320; j++){if((i * i -100) == (j * j -268)){number = i * i -100;if(number > 0){System.out.println(number + " ");}}}}}}14package work;import java.util.Scanner;public class Day{public static void main(String[] args){Scanner scanner = new Scanner(System.in);System.out.println("请输入年");int year = scanner.nextInt();System.out.println("请输入月");int month = scanner.nextInt();System.out.println("请输入日");int day = scanner.nextInt();boolean flag = false;if((((year % 4) == 0) && ((year % 100) != 0)) || ((year % 400) == 0)){ flag = true;}int sum = 0;switch(month){case 1 :sum = day; break;case 2 :sum = 28 + day; break;case 3 :sum = 59 + day; break;case 4 :sum = 90 + day; break;case 5 :sum = 120 + day; break;case 6 :sum = 151 + day; break;case 7 :sum = 181 + day; break;case 8 :sum = 212 + day; break;case 9 :sum = 243 + day; break;case 10 :sum = 273 + day; break;case 11 :sum = 304 + day; break;case 12 :sum = 335 + day; break;default :System.out.println("输入有误");}if(flag && (month > 1)){sum++;}System.out.println("这是一年中的第" + sum + "天");}}15package work;import java.util.Scanner;public class Min{public static void main(String[] args){Scanner scanner = new Scanner(System.in);System.out.println("请输入三个整数");int x = scanner.nextInt();int y = scanner.nextInt();int z = scanner.nextInt();if(x < y && x < z){System.out.print(x + " ");if(y < z){System.out.print(y + " " + z);}else if(y > z){System.out.print(z + " " + y);}}else if(y < x && y < z){System.out.print(y + " ");if(x < z){System.out.print(x + " " + z);}else if(x > z){System.out.print(z + " " + x);}}else if(z < y && z < x){System.out.print(z + " ");if(y < x){System.out.print(y + " " + x);}else if(y > x){System.out.print(x + " " + y);}}}}16package work;public class Nine{public static void main(String[] args){for(int i = 1; i <= 9; i++){for(int j = 1; j <= i; j++){System.out.print(j + " * "+ i + " = " + (j * i) + " ");}System.out.println();}}}17package work;public class Eat{public static void main(String[] args){System.out.println(eat(10,1));}public static int eat(int day, int sum){if(day == 1){return sum;}else if(day != 1){return eat(day - 1,(sum + 1) * 2);}return sum;}}18package work;public class Contest{public static void main(String[] args){char i, j, k;//a b c 的对手for(i = 'x'; i <= 'z'; i++){for(j = 'x'; j <= 'z'; j++){for(k = 'x'; k <= 'z'; k++){if(i != j && i != k && j != k){if(i != 'x' && k != 'x' && k!= 'z'){System.out.println(i + " " + j + " " + k);}}}}}}}19package work;public class Print{public static void main(String[] args){ for(int i = 0; i <= 4; i++){for(int j = 0; j < 4 - i; j++){System.out.print(" ");}for(int j = 0; j < 2 * i - 1; j++){System.out.print("*");}System.out.println();}for(int i = 3; i > 0; i--){for(int j = 0; j <= 3 - i; j++){System.out.print(" ");}for(int j = 0; j < 2 * i - 1; j++){System.out.print("*");}System.out.println();}}}20package work;public class Sum{public static void main(String[] args){ double[] a = new double[22];a[0] = 1.0;a[1] = 2.0;double sum = 0;for(int i = 2; i < 21; i++){a[i] = a[i - 1] + a[i - 2];}for(int i = 1; i < 21; i++){sum = sum + a[i] / a[i - 1];}System.out.println("sum = " + sum);}}21package work;public class Jiech{public static void main(String[] args){int sum = 0;for(int i = 1; i < 21; i++){sum = sum + jiech(i);}System.out.println("阶乘之和为：" + sum);}public static int jiech(int n){if(n == 1){return 1;}else if(n != 1){return jiech(n - 1) * n;}return 0;}}22package work;public class Jiecheng{public static void main(String[] args){System.out.println(jiech(5));}public static int jiech(int n){if(n == 1){return 1;}else if(n != 1){return jiech(n - 1) * n;}return 0;}}23package work;public class Age{public static void main(String[] args){System.out.println(age(5));}public static int age(int n){if(n == 1){return 10;}else if(n != 1){return age(n - 1) + 2;}return 0;}}24package work;import java.util.Scanner;public class Number{public static void main(String[] args){Scanner scanner = new Scanner(System.in);System.out.println("请输入一个不多于五位的正整数：");String num = scanner.next();int len = num.length();System.out.println("这是一个" + len + "位数");for(int i = len; i > 0; i--){System.out.println("第" + i + "位数是" + num.charAt(i - 1));}}}25package work;import java.util.Scanner;public class Huiwen{public static void main(String[] args){Scanner scanner = new Scanner(System.in);System.out.println("请输入一个五位数：");String number = scanner.next();if(number.charAt(0) == number.charAt(4) && number.charAt(1) == number.charAt(3)){System.out.println(number + "是回文数");}else{System.out.println(number + "不是回文数");}}}26package work;import java.util.Scanner;public class Week{public static void main(String[] args){Scanner scanner = new Scanner(System.in);System.out.println("请输入第1个字母：");String str = scanner.next();switch(str.charAt(0)){case 'm' :System.out.println("Monday"); break;case 't' :System.out.println("请输入第2个字母：");str = scanner.next();if(str.charAt(0) == 'u'){System.out.println("Tuesday");}else{System.out.println("Thursday");}break;case 'w' :System.out.println("Wednesday");break;case 'f' :System.out.println("Friday"); break;case 's' :System.out.println("请输入第2个字母：");str = scanner.next();if(str.charAt(0) == 'a'){System.out.println("Satday");}else{System.out.println("Sunday");}break;default :System.out.println("输入有误");}}}27package work;public class Prime{public static void main(String[] args){for(int i = 2; i < 100; i++){if(prime(i)){System.out.print(i + " ");}}}public static boolean prime(int number){boolean flag = true;for(int i = 2; i <= Math.sqrt(number); i++){if(number % i == 0){flag = false;}}return flag;}}28package work;public class Sort{public static void main(String[] args){int[] a = {2,4,3,6,7,8,1,89,56,23};sort(a);for(int array : a){System.out.print(array + " ");}}public static void sort(int[] a){int index;for(int i = 0; i < 9; i++){index = i;for(int j = i + 1; j < 10; j++){if(a[j] < a[index]){index = j;}}int t;if(index != i){t = a[i];a[i] = a[index];a[index] = t;}}}}29package work;import java.util.Scanner;public class Sum{public static void main(String[] args){Scanner scanner = new Scanner(System.in);int[][] a = new int[3][3];int sum = 0;System.out.println("请输入数据：");int i;for(i = 0; i < 3; i++){for(int j = 0; j < 3; j++){a[i][j] = scanner.nextInt();}sum = sum + a[i][i];}System.out.println("sum = " + sum);}}30package work;import java.util.Scanner;public class Sort{public static void main(String[] args){int[] a = new int[4];a[0] = 1;a[1] = 2;a[2] = 4;Scanner scanner = new Scanner(System.in);System.out.println("请输入一个整数：");int number = scanner.nextInt();if(number > a[a.length - 2]){a[a.length - 1] = number;}else{int k = 0;for(int i = a.length - 3; i > 0; i--){if(number > a[i]){k = i;}}for(int j = a.length - 1; j > k ; j--){a[j] = a[j - 1];}a[k + 1] = number;}for(int array : a){System.out.print(array + " ");}}}31package work;public class Array {public static void main(String[] args){int[] a = {1,2,3,4};int t;for(int i = 0; i < a.length / 2; i++){t = a[i];a[i] = a[a.length - i - 1];a[a.length - i -1] = t;}for(int array : a){System.out.print(array);}}}32package work;import java.util.Scanner;public class Move{public static void main(String[] args){Scanner scanner = new Scanner(System.in);System.out.println("请输入一个整数");String str = scanner.next();int len = str.length();System.out.println(str.charAt(len -4) + " " + str.charAt(len -5) + " " + str.charAt(len -6) + " " + str.charAt(len -7));}}33package work;public class Yanghui{public static void main(String[] args){int n = 6;int a[][] = new int[n][n];a[1][1] = 1;int i;for(i = 2; i < n; i++){a[i][1] = 1;a[i][i] = 1;for(int j = 2; j <= i; j++){a[i][j] = a[i - 1][j - 1] + a[i - 1][j];}}for(i = 1; i < n; i++){for(int j = 0; j < 5 - i; j++){System.out.print(" ");}for(int j = 1; j <= i; j++){System.out.print(a[i][j] + " ");}System.out.println();}}}34package work;import java.util.Scanner;public class Max {public static void main(String[] args){Scanner scanner = new Scanner(System.in);System.out.println("请输入a,b,c");int x = scanner.nextInt();int y = scanner.nextInt();int z = scanner.nextInt();if(x < y && x < z){System.out.print(x + " ");if(y < z){System.out.print(y + " " + z);}else if(y > z){System.out.print(z + " " + y);}}else if(y < x && y < z){System.out.print(y + " ");if(x < z){System.out.print(x + " " + z);}else if(x > z){System.out.print(z + " " + x);}}else if(z < y && z < x){System.out.print(z + " ");if(y < x){System.out.print(y + " " + x);}else if(y > x){System.out.print(x + " " + y);}}}}35package work;import java.util.Scanner;public class Maxmin {public static void main(String[] args){Scanner scanner = new Scanner(System.in);int[] a = new int[5];System.out.println("请输入数组值");int max = 0, min = 0, m = 0, n = 0, t = 0;for(int i = 0; i < a.length; i++){a[i] = scanner.nextInt();if(max < a[i]){max = a[i];m = i;}if(min > a[i]){min = a[i];n = i;}}t = a[0];a[0] = max;a[m] = t;t = a[4];a[4] = min;a[n] = t;for(int j = 0; j < a.length; j++){System.out.print(a[j] + " ");}}}36package work;import java.util.Scanner;public class Move{public static void main(String[] args){Scanner scanner = new Scanner(System.in);System.out.println("请输入5个数");int[] a = new int[5];int[] b = new int[5];for(int i = 0; i < 5; i++){a[i] = scanner.nextInt();}System.out.println("请输入移动的位数n");int n = scanner.nextInt();for(int j = 0; j < 5; j++){b[j] = a[(j + n) % 5];}for(int arr : b){System.out.print(arr + " ");}}}37package work;import java.util.Scanner;public class Stay{public static void main(String[] args){Scanner scanner = new Scanner(System.in);System.out.println("请输入人数n");int n = scanner.nextInt();boolean[] a = new boolean[n];for(int i = 0; i < a.length; i++){a[i] = true;}int rest = n;int count = 0;int i = 0;while(rest > 1){if(a[i] == true){count++;}if(count == 3){a[i] = false;rest--;count = 0;}i++;i = i % n;}for(i = 0; i < n; i++){if(a[i] == true){System.out.println(i);}}}}38package work;import java.util.Scanner;public class Length{public static void main(String[] args){Scanner scanner = new Scanner(System.in);System.out.println("请输入字符串");String str = scanner.next();System.out.println("长度为" + getLength(str));}public static int getLength(String s){return s.length();}}39package work;import java.util.Scanner;public class Sum{public static void main(String[] args){Scanner scanner = new Scanner(System.in);System.out.println("请输入一个数n");int n = scanner.nextInt();System.out.print("和为" + sum(n));}public static double sum(int n){double sum = 0;int k;if(n % 2 == 0){k = 2;}else{k = 1;}for(double i = k; i <= n; i = i + 2){sum = sum + 1.0 / i;}return sum;}}40package work;import java.util.Scanner;import java.util.Arrays;public class Sort{public static void main(String[] args){Scanner scanner = new Scanner(System.in);System.out.println("请输入一个字符串：");String str = scanner.next();char[] ch = str.toCharArray();Arrays.sort(ch);for(char c : ch){System.out.print(c);}}}41package work;public class Peach{public static void main(String[] args){System.out.println("共有桃子数目为：" + peach(5, 6));}public static int peach(int monkey, int sum){if(monkey == 1){return sum;}else if(monkey != 1){return peach(monkey - 1, sum * 5 + 1);}return 0;}}42package work;public class Number{public static void main(String[] args){for(int i = 10; i < 100; i++){if(809 * i == 800 * i + 9 * i + 1){System.out.println(i);}}}}43package work;public class Count{public static void main(String[] args){int n= 8;int one = n / 2;int two = (n - 1) * n / 2;int three = (n - 1) * n * n / 2;int four = (n - 1) * n * n * n / 2;int five = (n - 1) * n * n * n / 2;int six = (n - 1) * n * n * n * n / 2;int seven = (n - 1) * n * n * n * n * n / 2;int sum = one + two + three + four + five + six + seven;System.out.println(sum);}}44package work;import java.util.Scanner;public class Primer{public static void main(String[] args){Scanner scanner = new Scanner(System.in);System.out.println("请输入一个偶数");int n = scanner.nextInt();for(int i = 2; i <= n / 2; i++){if(primer(i) && primer(n - i)){System.out.println(n + " = " + i + " + " + (n - i));}}}public static boolean primer(int n){int i;for(i = 2; i <= n; i++){if(n % i == 0){break;}}if(i == n){return true;}else{return false;}}}45package work;//判断一个非素数能被几个9整除import java.util.Scanner;public class Nine{public static void main(String[] args){Scanner scanner = new Scanner(System.in);System.out.println("请输入一个合数");int number = scanner.nextInt();int count = 0;while(number % 9 == 0){number = number / 9;count++;}System.out.println("能被" + count + "个9整除");}}46package work;import java.util.Scanner;public class Connect{public static void main(String[] args){Scanner scanner = new Scanner(System.in);System.out.println("请输入两个字符串");String str1 = scanner.next();String str2 = scanner.next();String str3 = str1 + str2;System.out.println("连接后的字符串为" + str3);}}47package work;import java.util.Scanner;public class Print{public static void main(String[] args){Scanner scanner = new Scanner(System.in);System.out.println("请输入1--50之内的7个数");int[] a = new int[7];for(int i = 0; i < 7; i++){a[i] = scanner.nextInt();}for(int i = 0; i < 7; i++){System.out.println(a[i]);for(int j = 0; j < a[i]; j++){System.out.print("*");}System.out.println();}}}48package work;import java.util.Scanner;public class Secret{public static void main(String[] args){Scanner scanner = new Scanner(System.in);System.out.println("请输入四位整数：");int a = scanner.nextInt();int b = scanner.nextInt();int c = scanner.nextInt();int d = scanner.nextInt();System.out.println("加密后为" + jiaMi(d) + jiaMi(c) + jiaMi(b) + jiaMi(a));}public static int jiaMi(int num){num = (num + 5) % 10;return num;}}49package work;import java.util.Scanner;public class Str{public static void main(String[] args){Scanner scanner = new Scanner(System.in);System.out.println("输入一个字符串");String text = scanner.next();System.out.println("请输入一个子字符串");String str = scanner.next();String[] s = text.split(str);System.out.println((s.length - 1) + "次");}}50package work;import java.util.*;import java.io.*;public class Student {private String[] name = new String[5];private String[] number = new String[5];private int score[][] = new int[5][3];private int aver[] = new int[5];public static void main(String[] args)throws IOException{ Scanner scanner = new Scanner(System.in);Student student = new Student();File file = new File("d:\\stud.txt");FileWriter fw = new FileWriter("d:\\stud.txt");BufferedWriter bw = new BufferedWriter(fw);for(int i = 0; i < 5; i++){System.out.println("请输入姓名");[i] = scanner.next();bw.write(" "+[i]);System.out.println("请输入学号");student.number[i] = scanner.next();bw.write(" "+student.number[i]);int sum = 0;for(int j = 0; j < 3; j++){System.out.println("请输入成绩");student.score[i][j] = scanner.nextInt();bw.write( " "+student.score[i][j]);sum = sum + student.score[i][j];}student.aver[i] = sum / 3;bw.write(student.aver[i]);bw.newLine();}bw.close();}}。