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[英]Can we reverse a string by using maths logic without using for loop logic(starting with len-1) or built-in functions
[英]String palindrome without using built in functions
我想在不使用內置函數的情況下為字符串回文制作程序。
以下是我到目前為止嘗試過的代碼:
public class Palindrom
{
private static Scanner in;
public static void main(String[] args)
{
String s,str1,str2;
Scanner scan =new Scanner (System.in);
System.out.println("Enter the string");
String s = in.nextLine();
StringBuffer str1 = new StringBuffer();
StringBuffer str2 = new StringBuffer();
str1.reverse();
System.out.println("orignal string="+str2);
System.out.println("reveser string="+str1);
if(String.valueOf(str1).compareTo(String.valueOf(str2))==0)
System.out.println("palindrom");
else
System.out.println("not palindrom");
}
}
該程序無法正常運行。我認為問題出在in.nextLine
和字符串緩沖區中。
下面給出的是檢查在此處輸入的輸入代碼字符串是否為回文的最簡單方法。
import java.util.Scanner;
public class Strng {
public static void main(String[] args) {
String r = ""; //To store the reverse
Scanner sc = new Scanner(System.in);
System.out.println("Enter the String");
String s = sc.next(); // Entering the string
for(int i= s.length() - 1;i>=0;i--) {
r = r + s.charAt(i);
}
if(r.equals(s)) {
System.out.println("Is a palindrome");
}
else {
System.out.println("Not a palindrome");
}
}
}
public static void palindrome(String str){
Map<Character,Integer> myMap = new HashMap<Character, Integer>();
int characterCounter = 1;
int index=-1;
for(char ch : str.toCharArray()){
index++;
if(str.length()%2!=0 && index==Math.abs(str.length()/2)) continue;
if(myMap.containsKey(ch))
characterCounter = myMap.get(ch)+1;
myMap.put(ch, characterCounter);
}
boolean flag = true;
for(Character myMApVal: myMap.keySet()){
if(myMap.get(myMApVal)%2!=0){
flag=false;
break;
}
}
if(!flag) System.out.println(str+" is not palindrome");
else System.out.println(str+" is palindrome");
}
package practice;
import java.util.Scanner;
public class String_Palindrome {
public static void main(String[] args) {
//String s, str1, str2;
Scanner scanner = new Scanner(System.in);
System.out.println("Enter the string:");
String s = scanner.nextLine();
StringBuffer str1 = new StringBuffer(s);
StringBuffer str2 = new StringBuffer(s);
str1.reverse();
//System.out.println("Original String is:" + str2);
//System.out.println("Reverse String is:" + str1);
if (String.valueOf(str1).compareTo(String.valueOf(str2)) == 0)
System.out.println("Given String is a palindrome");
else
System.out.println("Given String is Not a palindrome");
}
}
下面的代碼是檢查字符串是否為回文的最簡單方法。
public class pal {
static String palindrome(String str) {
char[] array = str.toCharArray();
for (int i = 0; i < array.length / 2; i++) {
if (array[i] != array[array.length - i - 1]) {
return "not a palindrome ";
}
}
return "palindrome ";
}
public static void main(String args[]) {
System.out.println(palindrome("11211"));
}
}
import java.util.Scanner;
public class Palindrom {
static Scanner scanner = new Scanner(System.in);
public static void main(String[] args) {
System.out.println("Enter the string");
String inputStr =scanner.next();
System.out.println("Given String = "+inputStr);
char [] charArray=inputStr.toCharArray();
int strlength=(charArray.length)-1;
boolean isPalindrom=true;
for(int count=0; count<charArray.length && strlength >= 0; count++,strlength--){
if(charArray[count]!=charArray[strlength]){
isPalindrom=false;
break;
}
}
if(isPalindrom){
System.out.println("palindrom");
}else{
System.out.println("not palindrom");
}
}
}
說明:
取兩點
字符串 a[0] 的第一個開頭
字符串 a[length-1] 的第二個結尾
比較 char 數組中的每個 char
在循環時比較開始到結束和結束開始。
回文案例1:(長度為奇數)
“女士”是回文:
a[0] == a[4] 米
一[1] == 一[3] 一
a[2] == a[2] d
一[3] == 一[1] 一
a[4] == a[0] 米
回文案例2:(長度是偶數)
“馬拉雅拉姆語”是回文:
a[0] == a[8] 米
a[1] == a[7]
a[2] == a[6] l
一[3] == 一[5] 一
a[4] == a[4] 是
一[5] == 一[3] 一
a[6] == a[2] l
a[7] == a[1]
a[8] == a[0] 米
不是回文案例 3:在每個字符中都不匹配(開始到結束和結束開始)。
import java.util.Scanner;
public class StringPalindrome {
public static void main(String[] args) {
Scanner sc = null;
String str1 = null;
// create object for scanner class
sc = new Scanner(System.in);
if (sc != null) {
System.out.println("Enter First String");
str1 = sc.nextLine();
}
strPalindrom(str1);
}// main
static void strPalindrom(String str) {
// converting string into array
char ch[] = str.toCharArray();
// check string is Palindrom or not
int count = ch.length - 1;
for (int i = 0; i < ch.length; i++, count--) {
if (ch[i] != ch[count]) {
System.out.println("String is not Palindrom");
break;
} else {
if (i == count) {
System.out.println("String is Palindrom");
}
}
} // for
}// strPalindrom method
}// class
我看到了最重要的程序,但是對於初學者來說有點難以理解。
非常簡單的初學者程序(檢查字符串回文)
public class Palindrome{
public static void main(String[] args) {
String s = "malayalam"; // enter here your requred String to check Palindrom
String rev = "";
for (int i = s.length() - 1; i >= 0; i--) {
rev = rev + s.charAt(i);
}
if (rev.equals(s)) {
System.out.println("Palindrom");
} else {
System.out.println("Not Palindrom");
}
}
}
import java.util.*;
class Test{
public static void main(String... as){
int check=0;
Scanner s= new Scanner(System.in);
String str = s.nextLine();
int l=str.length();
for (int i=0;i<l;i++){
if(str.charAt(i)!=str.charAt(l-1-i))
check++;
}
if(check==0)
System.out.println("yes it's palindrome");
else
System.out.println("no it's not.");
}
}
public class Palindrom {
public static void main(String[] args) {
String str= "dad";
char[] rev=str.toCharArray();
int i=0;
int j= rev.length-1;
while(i<j){
char temp =rev[i];
rev[i] = rev[j];
rev[j] = temp;
i++;
j--;
}
System.out.println(rev);
System.out.println();
if(str.equals(String.valueOf(rev))){
System.out.println("Yes! It is palindrom");
}else{
System.out.println("No! It is not palindrom");
}
}
}
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