洛谷题P1009：使用高精度求阶乘。为什么for循环发生内存溢出了？该如何修改？要怎样避免？

Question

 
#include<bits/stdc++.h>
 
using namespace std;
 
int n, c[250],sum[250];
 
void pluss(int n,int b[])
{
    if (n == 1)  return ;
    int  a[250] = { -1 };
    for (int i = 0; n; i++)
    {
        a[i] = (n % 10);
        n /= 10;
    }
    
    for (int i = 1; a[i] != -1; i++)
    {
        for (int j = 1; b[j] != -1; j++)
        {
            c[i + j - 1] += a[i] * b[j];
            c[i + j] += (c[i + j - 1] / 10);
            c[i + j] %= 10;
        }
    }
 
    pluss(n - 1, c);  
}
 
int main()
{
    cin >> n;
    
    while (n)
    {
        int b[250] = { -1 };
        memset(b, -1, sizeof(b));
        b[1] = 1;
        pluss(n, b);
 
        for (int i = 1; i < 250; i++)
        {
            sum[i] += c[i];
            sum[i + 1] += (sum[i] / 10);
            sum[i] = (sum[i] % 10);
        }
 
        memset(c, 0, sizeof(c));
    }
 
    for (int i = 249; i > 1; i--)
    {
        if (sum[i] != 0)
        {
            for (int j = i; j > 1; j--)
            {
                cout << sum[j];
            }
            cout << '\n';
            return 0;
        }
    }
 
}

Answer 1

数组越界异常了。