Java进阶之欧拉工程 第八篇【持续更新】

原题如下：

The four adjacent digits in the 1000-digit number that have the greatest product are 9  9  8  9 = 5832.

73167176531330624919225119674426574742355349194934
96983520312774506326239578318016984801869478851843
85861560789112949495459501737958331952853208805511
12540698747158523863050715693290963295227443043557
66896648950445244523161731856403098711121722383113
62229893423380308135336276614282806444486645238749
30358907296290491560440772390713810515859307960866
70172427121883998797908792274921901699720888093776
65727333001053367881220235421809751254540594752243
52584907711670556013604839586446706324415722155397
53697817977846174064955149290862569321978468622482
83972241375657056057490261407972968652414535100474
82166370484403199890008895243450658541227588666881
16427171479924442928230863465674813919123162824586
17866458359124566529476545682848912883142607690042
24219022671055626321111109370544217506941658960408
07198403850962455444362981230987879927244284909188
84580156166097919133875499200524063689912560717606
05886116467109405077541002256983155200055935729725
71636269561882670428252483600823257530420752963450

Find the thirteen adjacent digits in the 1000-digit number that have the greatest product. What is the value of this product?

翻译：

在1000位数字，有最大的乘积的四个相邻的数字是9 9 8 9 = 5832。

找出以上这个1000位的整数中连续13个数字的最大乘积

解题思路：尼玛一看就头晕有么有！没办法，硬着头皮看了半天也没找出规律，那说明看是肯定看不出来的，所以应该想到将这些数字赋值到数组中去，然后通过比较前后13位数的乘积，找出最大的。在赋值到数组时发现这么多数字弄得我的程序简直丑陋不堪，于是我决定先存为txt文档，在用文件读取，取出来之后注意比较前后13位数的乘积取最大值，值得一提的是，由于乘积最后非常大，如果变量定义为int会造成溢出问题，我在写代码的时候也犯了这个错，想了好久才想明白，我果然还是太菜了，下面是代码：

public class Launcher {public static void main(String[] args) {ArrayList numList = new ArrayList();List v = new Vector();long sum=1L;FileReader fr=null;try {fr = new FileReader("X:/terribleNum.txt");} catch (FileNotFoundException e) {// TODO Auto-generated catch blocke.printStackTrace();}   int ch = 0;     try {for(int i =0;(ch = fr.read())!=-1;i++){v.add(ch-'0');}} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}    for(int i=0;i<v.size()-12;i++){for(int j=i;j<i+13;j++){sum =sum *(int)v.get(j);}System.out.println(sum); numList.add(sum);  sum=1;}Collections.sort(numList);//为了排序引入的函数System.out.println(numList.get(numList.size()-1));   }}