close
401
import java.util.Scanner;
public class JPA04 {
static Scanner keyboard = new Scanner(System.in);
public static void main(String args[]) {
System.out.print("Input n (0 <= n <= 16):");
int n = keyboard.nextInt();
while(n!=999){
if(n!=999){ //若 n 不為 999 則打印其內容
System.out.printf("%d 的階乘 = %d\n",n,factorial(n));
}
System.out.print("Input n (0 <= n <= 16):");
n = keyboard.nextInt();
}
}
static int factorial(int y){ //自訂一個遞迴方法
if(y==0){ //若傳入 0 ，則返回 1
return 1;
}else{ // 傳入任意數字，則將他 遞迴的 乘上本身減1，
return (y * factorial(y-1));
}
}
}
402
import java.util.Scanner;
public class JPA04 {
static Scanner keyboard = new Scanner(System.in);
public static void main(String args[]) {
System.out.print("Input n (0 <= n <= 16):");
int n = keyboard.nextInt();
int sum = 1; // 題目規定要另外傳入參數來累計遞迴的答案
while(n!=999){
System.out.printf("%d 的階乘(尾端遞迴) = %d\n",n,fac(n,sum));
System.out.printf("%d 的階乘(迴圈) = %d\n",n,loop(n));
System.out.print("Input n (0 <= n <= 16):");
n = keyboard.nextInt();
}
}
static int fac(int x, int sum){ //尾端遞迴：在返回值時調用自己
if (x == 0) return sum; //若 x 為 0，返回 1
else return fac(x-1,x*sum);//若 x 不為 0，則將 x-1 再次帶入遞迴
}
static int loop(int y){
int sum = 1;
while(y>0){ //迴圈
sum = y * sum;
y = y -1; //每迴圈一次，減少1，直到為 0 停止
}
return sum;
}
}
403
import java.util.Scanner;
public class JPA04 {
static Scanner keyboard = new Scanner(System.in);
public static void main(String args[]) {
System.out.print("Input m:");
int sum =1; //設一變數為累積遞迴的答案
int m = keyboard.nextInt();
while(m != 999){ //若 m 為 999 時，則跳出迴圈
System.out.print("Input n:"); //由於輸入 m 後就要判定是否運行迴圈，所以 n 要放入迴圈之中
int n = keyboard.nextInt();
System.out.printf("Ans (尾端遞迴) : %d\n",fac(m,n,sum));
System.out.printf("Ans (迴圈) : %d\n",loop(m,n));
System.out.print("Input m:");
m = keyboard.nextInt();
}
}
static int fac (int x, int y,int sum){ //尾端遞迴
if (y == 1) return x * sum; // y = 1 時就停止，=0的話會多乘一次
else return fac(x,y-1,x*sum); //尾端遞迴，在結尾呼叫自己
}
static int loop (int a, int b){ //迴圈
int sum =1; //設一變數存放最後值
while (b > 0){ //若大於 0 就繼續運行
sum = sum * a; //每次迴圈乘上一次 a
b = b - 1; //每次迴圈，次方數減少 1
}
return sum; //返回最後值
}
}
404
import java.util.Scanner;
public class JPA04 {
static Scanner keyboard = new Scanner(System.in);
public static void main(String args[]) {
System.out.print("Input m: ");
int m = keyboard.nextInt();
while(m!=999){
System.out.print("Input n: ");
int n = keyboard.nextInt();
System.out.printf("最大公因數為：%d\n",gcd(m,n)); //呼叫自訂函數 gcd
System.out.print("Input m: ");
m = keyboard.nextInt();
}
}
static int gcd(int x, int y){
if (x % y == 0){ //若 餘數為0 則返回 y
return y;
}else{ //若 餘數不為0 則輾轉相除
return gcd(y,x%y);
}
}
}
405
import java.util.Scanner;
public class JPA04 {
static Scanner keyboard = new Scanner(System.in);
public static void main(String args[]) {
System.out.print("Input the number n: ");
int n = keyboard.nextInt();
if(n>=1) //題目要求 n >=1
System.out.printf("Ans: %d",sum2(n));
}
static int sum2(int x){
if(x == 1) return 2; //題目要求，若sum2 = 1，則返回 2
else{
return sum2(x -1) + 2 * x; //依照題目公式
}
}
}
406
import java.util.Scanner;
public class JPA04 {
static Scanner keyboard = new Scanner(System.in);
public static void main(String args[]) {
System.out.print("Input a a string: ");
String x = keyboard.nextLine(); //讀取整行字串
System.out.printf("%s has %d As\n",x,countA(x));
System.out.print("Input a a string: ");
x = keyboard.nextLine();
System.out.printf("%s has %d As\n",x,countA(x));
}
public static int countA(String str) {
if(str.equals("")) return 0; //若字串沒有內容，則返回0
else if(str.substring(0,1).equals("A"))//若字串第1個字為A，
return 1 + countA(str.substring(1)); //則返回 1 + 從字串第2個字開始的內容(ex.若為"Apple" 則返回 1 + "pple")
else return countA(str.substring(1)); //若字串第1個字不為A，則返回第一個字元後之後的所有內容
}
}
//string.equals(x) 比較字串與x是否相同
//string.substring(x,y) 取出字串中 第 x 到第 y 個字元的字串
//string.substring(x) 取出字串中 第 x 個字元之後的字串
407
import java.util.Scanner;
public class JPA04 {
static Scanner keyboard = new Scanner(System.in);
public static void main(String args[]) {
String s;
System.out.print("Input a string of numbers: ");
s = keyboard.nextLine();
System.out.printf("尾端遞迴：%d\n", sumTail(s, 0));
System.out.printf("迴圈：%d\n", sumLoop(s, 0));
System.out.print("Input a string of numbers: ");
s = keyboard.nextLine();
System.out.printf("尾端遞迴：%d\n", sumTail(s, 0));
System.out.printf("迴圈：%d\n", sumLoop(s, 0));
}
// Integer.parseInt(String s) 將字串解析為十進位整數
static int sumTail(String x, int y){
if (x.equals("")) return y; //若字串已經無內容，則返回 y
else{
y = y + Integer.parseInt(x.substring(0,1)); //將第一個整數取得，加總到y上
return sumTail(x.substring(1), y);
}
}
// String.length() 取得字串長度
static int sumLoop(String a, int b){
for(int i =0;i<a.length();i++){
b = b + Integer.parseInt(a.substring(i,i+1)); //將第一個整數取得，加總到b上
}
return b;
}
}
408
import java.util.Scanner;
public class JPA04 {
static Scanner keyboard = new Scanner(System.in);
public static void main(String args[]) {
String s, c;
System.out.print("Input a string: ");
s = keyboard.nextLine();
System.out.printf("%s\n", reverse(s));
System.out.print("Input a string: ");
s = keyboard.nextLine();
System.out.printf("%s\n", reverse(s));
}
static String reverse(String x){
if (x.equals("")) return ""; //若字串已無內容，則返回空值
else return reverse(x.substring(1))+x.substring(0,1);//返回 "遞迴(第二個字元開始的字串)"，在尾端加上第一個字元
}
}
409
import java.util.Scanner;
public class JPA04 {
static Scanner keyboard = new Scanner(System.in);
public static void main(String args[]) {
String s, c;
System.out.print("Input a string: ");
s = keyboard.nextLine();
System.out.print("Input a character: ");
c = keyboard.nextLine();
System.out.printf("%s\n", removeChar(s, c));
System.out.print("Input a string: ");
s = keyboard.nextLine();
System.out.print("Input a character: ");
c = keyboard.nextLine();
System.out.printf("%s\n", removeChar(s, c));
}
static String removeChar(String x, String y){
if (x.equals("")) return ""; //若該字串已無內容，則返回空值
else if (x.substring(0,1).equals(y)) return removeChar(x.substring(1),y); //若第一個字元等於要移除的字元，則返回removeChar(第二個字元開始, 要移除的字元)
else return x.substring(0,1) + removeChar(x.substring(1),y); //若第一個字元有內容且不等於要移除的字元，則返回 (第一個字元 + removeChar(第二個字元開始, 要移除的字元))
}
}
410
import java.util.Scanner;
public class JPA04 {
static Scanner keyboard = new Scanner(System.in);
public static void main(String args[]) {
String s, c1, c2;
System.out.print("Input a string: ");
s = keyboard.nextLine();
System.out.print("Input a character: ");
c1 = keyboard.nextLine();
System.out.print("Input another character: ");
c2 = keyboard.nextLine();
System.out.printf("%s\n", replace(s, c1, c2));
}
static String replace(String a, String b, String c){
if (a.equals("")) return ""; //若字串已無內容，則返回空值
else if(a.substring(0,1).equals(b)){ //若第一個字元等於要被替換的字元
return c + replace(a.substring(1),b,c);//返回 (替換上的字元 + replace(第二個字元開始,要被替換的字元,替換上的字元))
}
else{
return a.substring(0,1) + replace(a.substring(1),b,c);//返回 (第一個字元 + replace(第二個字元開始,要被替換的字元,替換上的字元))
}
}
}
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