分割故障（核心转储）的快速联盟Implementaion C语言 [英] Segmentation fault (core dumped) in Quick Union Implementaion in C

问题描述

#include<stdio.h>
#include<stdlib.h>
int *id,N;

main()
{
    FILE* file=fopen("a.txt","r");
    int i,p,q,c;
    fscanf(file,"%d",&N);

    id=(int *)malloc(N*sizeof(int));

    for(i=0;i<N;i++)
        *(id+i)=i;

    while(!feof(file))
    {
        fscanf(file,"%d %d",&p,&q);
        if(!connected(p,q))
            unn(p,q);
    }
    fclose(file);
    c=1;

    while(c==1)
    {
        scanf("%d %d",&p,&q);
        printf("%d\nYes(1) or No(0)    ",connected(p,q));
        scanf("%d",&c);
    }
}

connected(int p,int q)
{
    return((root(p))==(root(q)));
}

unn(int p,int q)
{
    int j=root(q);
    int i=root(p);
    *(id+j)=i;
}

root(int i)
{
    while(i!=(*(id+i)))
        i=*(id+i);
    return(i);
}

在编译时，不显示错误消息。但是，当我尝试执行这个程序，它说：分段错误（核心转储）。为什么会出现这种情况？ 由于可能已经注意到，这是实施快速联合的尝试。

On compiling, no error message is displayed. However, when I try to execute this program, it says"Segmentation Fault (core dumped). Why does this happen? As may have noticed, this is an attempt to implement the quick union.

快速查找未经使用相同的文件a.txt中只用了一些调整，以这种code任何麻烦来实现。 *的是或否是用于用户的查询。

The quick find was implemented without any hassle using the same file "a.txt" with only a few tweaks to this code. * The Yes or No is for the user's query.

推荐答案

我猜这就是问题所在。

root(int i)
{
    int p;  
    while(p!=(*(id+p)))   <-- p uninitialised 
        p=*(id+p);
    return(p);
}

由于 P 是未初始化的，但你正在使用它作为一个指针引用的偏移量。即使这不是原因，它仍然是一个大问题。

because p is uninitialised but you are using it as an offset in a pointer dereference. Even if it is not THE reason it is still a big problem.

您已经从编辑的问题离开

You have since edited the question to leave

root(int i)
{
    int i;  
    while(i!=(*(id+i)))  
        i=*(id+i);
    return(i);
}

在您重新定义了我变量本地以及传递函数参数我变量。

in which you redeclare an i variable locally as well as a i variable passed as function parameter.

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