基于链表的多项式乘法程序段错误问题排查及scanf是否会引发段错误的疑问

Hey there! Let's break down your segmentation fault issue and address your scanf concern step by step.

First, let's clear up your scanf question: No, your current scanf statements aren't causing the segmentation fault. The scanf("%d%d",&co1,&po1); line uses valid addresses for your integer variables (co1 and po1 are properly declared in main), so scanf itself won't trigger a crash here. The issue lies elsewhere in your code.

The Critical Bug Causing Segmentation Faults #

Looking at your addterms function, there's a major flaw in the code that adds new terms to the result list when there's no matching power:

if(flag==0)
{
    cur=res;
    while(cur!=NULL)
    {
        cur=cur->add;
    }
    cur->add=temp; // Crash happens here!
}

When this code runs, the loop continues until cur becomes NULL (after reaching the end of the list). Trying to access cur->add when cur is NULL is a classic null pointer dereference, which directly triggers a segmentation fault.

To fix this, change the loop condition to stop at the last valid node (instead of going past it):

if(flag==0)
{
    cur=res;
    while(cur->add != NULL) // Stop at the last node with a non-null next pointer
    {
        cur=cur->add;
    }
    cur->add=temp; // Now cur points to the last valid node, safe to modify its add
}

This bug will trigger when your multiply function tries to add a new unique power term, which explains why you're seeing crashes during polynomial operations.

Addressing Your Immediate Crash During Input #

You mentioned the crash happens when entering the last term of the second polynomial. While your insert function looks correct, there's a possibility that:

• The crash is actually happening later in the display or multiply steps, but buffered output makes it seem like it's happening during input (since your printf("Insert"); doesn't include a newline, so the message might not flush to the console before the crash).
• A leftover core dump from a previous run is confusing your test results.

After fixing the addterms bug, recompile and test your program again. This should resolve the segmentation fault issues you're seeing.

Additional Minor Improvements #

• Add newlines to your printf statements (e.g., printf("Enter the number of polynomial terms\n");) to make input/output cleaner and avoid buffered output confusion.
• In the addterms function, once you find a matching power, you can break out of the loop early to save some computation:

  while(cur!=NULL)
  {
      if(cur->po==po)
      {
          cur->co=cur->co+co;
          flag=1;
          break; // No need to check further terms
      }
      cur=cur->add;
  }
  

备注：内容来源于stack exchange，提问作者Hammish Raj Wadeyar