分割错误C++（数组太大？）

我正在研究欧拉项目Problem 14，我需要找到1,000,000下最长的collatz序列。我想出了一种适用于较小数字（比如100）的算法，该算法将每个1到100之间的collatz数存储到一个数组中，并将该数组用作参考，以加快计算数量。我的代码如下：分割错误C++（数组太大？）

#include <iostream> 
using namespace std; 

long even(long n){ //the even-collatz function 
    n=n/2; 
    return n; 
} 

long odd(long n){ //the odd collatz function 
    n=3*n+1; 
    return n; 
} 

int main(){ 
    long x, c=0, y[1000000]; // x= the number we are finding the collatz number of, c a counter that keeps track of how many steps we've taken in the sequence, y is an array to store the collatz numbers. 

    for (x=1; x<1000000; x++){ //iterates from x=1 to 1 million 
      long a = x;  //sets a number a equal to the number we are currently trying to find the collatz number of 
      long b = a;  
      c=0;     //intializes counter at 0 
      while (a!=0){   //loops infinitely; the only way to exit is through a break. 
        if (a%2==0){ // detects if the number is even 
          a=even(a);  //applies the even-collatz function if so; sets x=x/2 
          c=c+1; 
          if (y[a]!=0){ // checks if the collatz number of x is already discovered 
            y[b]=c+y[a]; //adds the current number of steps to the collatz number of x and 
            break; //exits the while loop 
          } 

        } 
        else if (a==1){   //checks if the new x is equal to one and 
          y[b]=c;   //if it is, it writes the current value of c to y[b] and 
          break;   // exits the loop 
        } 
        else if (a%2==1){  //same as the "even" block, except for odd numbers 

          a=odd(a); 
          c=c+1; 
          if(y[a]!=0){ 
            y[b]=c+y[a]; 
            break; 
          } 

        } 
      //this is the end of the while loop; we've applied the collatz function as many times as we've needed to to x, and incremented the counter each time 
      } 
    } 

    long z; 
    for (int n=0;n!=100;n++){ 
      if (y[n+1]>y[n]){ 
        z=y[n+1]; 
      } 
    } 
    cout << z << "\n"; 


}

我遇到的问题是，我得到一个segfault在x = 1818在for循环。通过调试，我发现段错误发生的速度取决于数组y的大小，所以我假设该数组太大了。从我对segfaults的基本理解来看，我认为我只是访问了我“不被允许”的内存。有什么方法可以绕过这个问题吗？或者我应该开始努力寻找解决这个问题的另一种解决方案吗？我正在Ubuntu Studio上使用g ++进行编译。

来源

2014-09-28 Peter Dragos