知识树中的段错误 [英] Seg Fault in Knowledge Tree

问题描述

我正在用 c 语言实现一个可以从文件中读取的知识树.我的 newStr 函数出现段错误.我无法用这个问题测试我的其余代码.我对c没有太多经验.任何帮助将不胜感激.

I am implementing a knowledge tree in c that can read from a file. I am getting a seg fault in my newStr function. I'm not able to test the rest of my code with this problem. I don't have much experience with c. Any help would be greatly appreciated.

我的.c文件#包括#包括#include"animal.h"#包括#include

my .c file #include #include #include"animal.h" #include #include

/*returns a new node for the given value*/
struct Node * newNode (char *newValue) 
{
struct Node * tree;
tree = (struct Node*)malloc(sizeof(struct Node));
tree -> value = newStr(newValue);
return tree;
}


/* returns a new string with value passed as an argument*/
char * newStr (char * charBuffer)
{
int i;
int length = strlen(charBuffer);
char newStr;
if(charBuffer[0] == 'A' || charBuffer[0] == 'Q'){
    for(i=1; i<length; i++)
        newStr += charBuffer[i]; 
}
return (newStr + "");
}

/*Read from a File and create a tree*/
struct Node * readATree(FILE * f)
{
  char c;
  char buffer[100];
  struct Node * newTree;
  c = fgetc(f);
  if (c == 'A'){
     fgets(buffer, 100, f);
     newTree = newNode(buffer);
     newTree -> left = NULL;
     newTree -> right = NULL;
    }
  else{
     fgets(buffer, 100, f);
     newTree = newNode(newStr(buffer));
     newTree->left = readATree(f);
     newTree->right = (struct Node *) readAtree(f);
     }
  return newTree;

}

/*Write Tree to a File*/
void writeAFile(struct Node* tree, FILE * f)
{
    char buffer[100];
    strcpy(buffer, tree->value);
    if(tree != 0){
        if(tree->left == NULL && tree->right == NULL){
            fputc((char)"A", f);
            fputs(buffer,f);
        } else{
            fputc((char)"Q",f);
            fputs(buffer,f);
            writeAFile(tree->left, f);
            writeAFile(tree->right,f);
        }
    }
}

/*The play should start from here*/
int main (){
    struct Node* node;
    struct Node* root;
    char ans[100];
    char q[100];
    FILE * f;
    f = fopen("animal.txt", "r+");
    if(f != NULL)
        readATree(f);
    else{
        node = newNode("Does it meow?");
    node->right = NULL;
    node->right->right=NULL;
    node->left->left=NULL;
    node->left=newNode("Cat");
    root = node;
}
while(node->left != NULL && node->right != NULL){
    printf(node->value);
    scanf(ans);
    if(ans[0] == (char)"Y" || ans[0] == (char)"y")
        node = node->left;
    else if(ans[0] == (char)"N" || ans[0] == (char)"n")
        node = node->right;
    else
        printf("That is not a valid input.
");
}
if(ans[0] == (char)"Y" || ans[0] == (char)"y")
    printf("I win!");
else if(ans[0] == (char)"N" || ans[0] == (char)"n"){
    printf("What is your animal");
    scanf(ans);
    printf("Please enter a yes or no question that is true about %s?
", ans);
    scanf(q);
    node->right = newNode(q);
    node->right->left = newNode(ans);
    node->right->right = NULL;
}
writeAFile(root,f);
fclose(f);
return 0;
}

.h 文件#include

.h file #include

struct Node {
char *value;
struct Node * left;
struct Node * right;
};

struct Node * newNode (char *newValue) ;
char * newStr (char * charBuffer);
struct Node * readATree(FILE * f);
void writeAFile(struct Node* tree, FILE * f);

推荐答案

可能还有几个，但这里有一些问题的要点:

There might be several more, but here's some points on what's wrong:

1. 你的 newStr 函数非常，非常错误.估计你会想要类似:

1. Your newStr function is just very, very wrong. At a guess you'd want something like:

char * newStr (char * charBuffer)
{
  char *newStr;
  if(charBuffer[0] == 'A' || charBuffer[0] == 'Q') {
    newStr = strdup(&charBuffer[1]);
  } else {
    newStr = strdup("");
  }
  if(newStr == NULL) {
      //handle error
  }
  return newStr;
}

不能将字符串转换为字符就像你在这里做的一样:

You can't cast a string to a char like you do here:

 if(ans[0] == (char)"Y" || ans[0] == (char)"y")

改为执行(类似代码相同其他地方也一样)

Do instead(same for similar code elsewhere too)

 if(ans[0] =='Y' || ans[0] == 'y')

和上面调用putc时一样，不要做

Same as above when you call putc, don't do

 fputc((char)"A", f);

做

 fputc('A', f);

scanf 需要格式字符串，不要做:

scanf needs a format string, don't do:

scanf(ans);

做例如(或者只是再次使用 fgets)

Do e.g. (or just use fgets again)

if(scanf("%99s",ans) != 1) {
   //handle error
 }

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