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;
    } 40 }

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();
    }
}