c++ - 为什么我会收到大整数的分段错误？

Question

我写了一段代码如下：

#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    long long int n,s,p,q,i;
    cin>>n>>s>>p>>q;
    long long int a[n];
    a[0] = s%(long long int)pow(2,31);
    for(i=1;i<n;i++)
    {
        a[i] = a[i-1]*p+s%(long long int)pow(2,31);
    }
    long long int count=1;
    for(i=1;i<n;i++)
    {
        if(a[i]!=a[i-1])
        count++;
    }
    cout<<count;
    return 0;
}

当我提供输入时出现分段错误

100151543 5115 5153 531 stderr如下：

    Reading symbols from Solution...done.
[New LWP 134199]
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Core was generated by `./Solution'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x00000000004010f1 in main () at Solution.cpp:13
13      a[0] = s%(long long int)pow(2,31);
To enable execution of this file add
    add-auto-load-safe-path /usr/local/lib64/libstdc++.so.6.0.25-gdb.py
line to your configuration file "//.gdbinit".
To completely disable this security protection add
    set auto-load safe-path /
line to your configuration file "//.gdbinit".
For more information about this security protection see the
"Auto-loading safe path" section in the GDB manual.  E.g., run from the shell:
    info "(gdb)Auto-loading safe path"

问题是hackerrank：https ://www.hackerrank.com/challenges/bitset-1/problem

标签： c++segmentation-faultc++14

Answer 1

long long int a[n];

不会对你有任何好处，就像每个人都说最好使用向量，你的代码应该是这样的：

#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    long long int n,s,p,q,i;
    cin>>n>>s>>p>>q;
    vector<long long int> a;
    a.resize(n);
    a[0] = s%(long long int)pow(2,31);
    for(i=1;i<n;i++)
    {
        a[i] = a[i-1]*p+s%(long long int)pow(2,31);
    }
    long long int count=1;
    for(i=1;i<n;i++)
    {
        if(a[i]!=a[i-1])
        count++;
    }
    cout<<count;
    return 0;
}