项目Euler＃8的代码不起作用

Question

我花了几个小时努力解决这个问题，我只是想不通为什么它不起作用。基本上，问题是找到具有最大总和的十三个连续数字。如果我修改它以寻找四位数或五位数，它会得到正确的答案，但当它找到十三时我得到2091059712，这是不正确的。我对编码很陌生，对于可能出错的事情我完全不知所措。

// this is the 1000 digit number
String big = "73167176531330624919225119674426574742355349194934" +
        "96983520312774506326239578318016984801869478851843"+
        "85861560789112949495459501737958331952853208805511"+
        "12540698747158523863050715693290963295227443043557"+
        "66896648950445244523161731856403098711121722383113"+
        "62229893423380308135336276614282806444486645238749"+
        "30358907296290491560440772390713810515859307960866"+
        "70172427121883998797908792274921901699720888093776"+
        "65727333001053367881220235421809751254540594752243"+
        "52584907711670556013604839586446706324415722155397"+
        "53697817977846174064955149290862569321978468622482"+
        "83972241375657056057490261407972968652414535100474"+
        "82166370484403199890008895243450658541227588666881"+
        "16427171479924442928230863465674813919123162824586"+
        "17866458359124566529476545682848912883142607690042"+
        "24219022671055626321111109370544217506941658960408"+
        "07198403850962455444362981230987879927244284909188"+
        "84580156166097919133875499200524063689912560717606"+
        "05886116467109405077541002256983155200055935729725"+
        "71636269561882670428252483600823257530420752963450";
ArrayList<Integer> nums = new ArrayList<Integer>();
int counter = 0;
    for (counter = 0; counter<988; counter++) {
        String str = big.substring (counter,counter+13);
// creates a substring thirteen digits long
        Integer product = 1;
        for (int o=0; o<13; o++) {
            String num = Character.toString(str.charAt(o));
            Integer numb = Integer.parseInt(num);
// Turns each digit into an integer and then multiplies them together
            product = product*numb;
        }
            nums.add(product);
        }
//finds biggest number
int bignum = 0;
for (Integer num : nums) {
    if (num > bignum) {
        bignum = num;
    }
}

非常感谢任何帮助。感谢。

Answer 1

将所有整数更改为长整数，唯一的问题是整数存储。

Answer 2

您需要将numb和bignum更改为Longs而不是Ints，如果那些不起作用，那么您可以将它们更改为BigIntegers。