POJ 1047 Round and Round We Go 最详细的解题报告

题目链接:Round and Round We Go

解题思路：用程序实现一个乘法功能，将给定的字符串依次做旋转，然后进行比较。由于题目比较简单，所以不做过多的详解。

具体算法（java版，可以直接AC）

 import java.util.Scanner;

 public class Main {

     public static void main(String[] args) {
         Scanner scanner = new Scanner(System.in);
         String line;
         while (scanner.hasNext()) {
             line = scanner.next();
             MyNumber number = new MyNumber(line);
             int count = 0;
             for (int i = 2; i <= line.length(); i++) {
                 NumNode[] result = number.multiply(i);
                 if (number.isCycle(result)) {
                     count++;
                 }
             }
             if (count == line.length()-1) {
                 System.out.println(line + " is cyclic");
             } else {
                 System.out.println(line + " is not cyclic");
             }
         }
     }

 }

 class NumNode {
     int value;
     int carry;

     public NumNode() {
         this.value = 0;
         this.carry = 0;
     } }

 class MyNumber {
     private NumNode[] data;
     private int length;
     private String[] rotation;
     private boolean isRotated;

     public MyNumber(String line) {
         this.length = line.length();
         this.isRotated=false;
         this.data = new NumNode[this.length];
         this.rotation = new String[this.length];
         for (int i = this.length - 1; i >= 0; i--) {
             this.data[i] = new NumNode();
             this.data[i].value = line.charAt(i) - '0';
         }
     }

     private void rotate() {
         for (int i = 0; i < this.length; i++) {
             StringBuffer buffer = new StringBuffer();
             for (int j = i; j < this.length; j++) {
                 buffer.append(this.data[j].value);
             }
             for (int j = 0; j < i; j++) {
                 buffer.append(this.data[j].value);
             }
             this.rotation[i] = buffer.toString();
         }
     }

     public NumNode[] multiply(int a) {
         NumNode[] result = new NumNode[this.length];
         for (int i = this.length - 1; i >= 0; i--) {
             int value = this.data[i].value * a;
             result[i] = new NumNode();
             if (i + 1 < this.length) {
                 value += result[i + 1].carry;
             }
             result[i].value = value % 10;
             result[i].carry = value / 10;
         }
         return result;
     }

     public boolean equals(String s) {
         for (String str : this.rotation) {
             if (str.equals(s))
                 return true;
         }
         return false;
     }

     public boolean isCycle(NumNode[] num) {
         if (num[0].carry > 0)
             return false;
         if(!this.isRotated){
             this.rotate();
             this.isRotated=true;
         }
         StringBuffer buffer = new StringBuffer();
         for (int i = 0; i < num.length; i++) {
             buffer.append(num[i].value);
         }
         return this.equals(buffer.toString());
     }

     public String toString() {
         StringBuffer buffer = new StringBuffer();
         for (int i = 0; i < this.length; i++) {
             buffer.append(this.data[i].value);
         }
         return buffer.toString();
     }
 }